Been thinking more about this topic, and decided to add some more comments and thoughts, because this is actually something for which I have a good deal of interest.
I do not believe that a really good quality jian is commercially available. At least not anything that is manufactured in quantity, including the Paul Chen stuff, and anything coming out of China.
The vast majority of what is available it of very poor quality material, as well as very poor quality workmanship, and I'll explain step-by-step.
First, the blade. Most things on the market are super-light and meant for modern wushu. These are not real weapons. They are little more than a stage prop, meant to give the impression that the wushu people are using weapons. But they are not real. They are not made of quality steel, often are not made of steel at all, and would not stand up to the very first clash with a real weapon. They are often flexible in the extreme, to the point where you would turn the blade into an accordion if you tried to thrust it into virtually anything. To give credit, the very thinness of these blades can make them somewhat dangerous, as you can get cut by them, at least the ones that are made out of thin steel. Personally, I stopped playing with toy swords when I was about 12, and that is what these are.
Some blades on the market give the impression of being a real, combat quality piece. But these are often over-heavy, unwieldy, clunky, and are again made of the wrong kind of steel, including stainless steel. A heavy, clumsy blade is also not a real weapon, altho if you train with one you might develop your strength. I would choose one of these over a light wushu piece, (altho not if it was stainless steel) if that was the only choice available to me. But understand that it is just a training piece, taking advantage of the extra weight. Any sword over 2 1/2-3 pounds for a single-hander, or about 4-4 1/2 pounds for a two-hander, is pushing the limits.
The guard: most guards are of inferior materials. Many are actually made of a wood core, with a piece of brass sheeting covering it to appear that it is made of metal. This has no weight to it and does nothing to help balance the blade. It also has no strength, and would likely split away at the first strike from a real weapon. Some guards are actually made of metal (the Paul Chen pieces come to mind), but are of an inadequate design. The metal is insubstantial and of a thin, sort of skeletal design rather than a thick, solid piece that might actually give your hand some level of protection if the enemy's weapon struck against it.
The pommel: many pommels share the same problems as outlined with the guards. Some are made of a wood core, with a sheet of brass covering. Again, no weight to balance the blade, no strength to survive a real strike (the pommel can be used to punch or bludgeon the enemy). Others have a fancy skeletal design, that again lack weight and strength to stand up to a solid strike. A pommel needs to be somewhat weighty, as well as solid and strong.
The workmanship: Many swords on the market, particularly those coming out of China and priced very low: $30-$100, have awful workmanship in assembly. The guard, grip, and pommel fit poorly onto the blade, and are inadequately secured with a small hex nut behind the pommel. The pieces do not match cleanly, and have the appearance that they were just haphazardly jammed onto the blade. It's really shameful.
The scabbard: many scabbards have ugly brass sheeting as design and to hold the wood slats together. These have a way of coming loose and even sliding off. I examined one scabbard where the end piece came off, and I could see that underneath it the wood slats did not even fully meet and seal the encasement.
What makes a good sword: Start with a blade made of quality steel (in most cases, this excludes stainless steel, altho I've read that if a swordsmith knows what he is doing, a good blade can be made from the right kind of stainless). At any rate, this should be a high quality carbon steel, preferably with some amount of flex, but not too floppy. A really good quality modern alloy steel is 5160, which is used to make flat springs for truck suspensions. It's a very tough steel, takes a good edge, and has a stiff springiness to it.
The blade should be beefy enough to be strong, but not over heavy. A heavy clunker just doesn't handle well.
The guard and pommel need to be made of solid metal, such as steel or bronze. A silver alloy can be used, I've made a couple that way, but it is definitely expensive. If done properly, the silver alloy can have a similar strength to bronze, but it's heavier. You will get more weight, maybe 15%-20% more, out of a pommel or guard of the same size. These pieces must be solid and beefy enough to take a beating, and also balance the blade.
The grip needs to be shaped into a comfortable size and shape. I tend to leave them bare, finishing them with an oil finish, but some people like to cover them in wraps or leather. This can give a better grip, but I like the look of the wood.
All these pieces need to be fitted well together, so that where they meet is clean and smooth. They need to be firmly attached, with a hefty hex nut or something similar, behind the pommel, or it can be peened on to make it permanent. Also, I sometimes will cover the tang with epoxy so that the entire hilt is permanently fixed onto the blade. This is in addition to the nut behind the pommel. I wouldn't trust epoxy all by itself. If it failed, the blade could fly out of the handle in use.
At any rate, these are the things to keep in mind with a good jian, and to find all the elements together in one piece is a rarity, unless it's been custom built. In my opinion, the only way to get a good jian is to have it custom built. Anything being done in high quantity is likely to be disappointing in some way or other. Some things really ought to be done one at a time, and not mass-produced.