Cart update: old TT, new electronics

You are in a rare catagory. Most people would consider your table (and arm) way below the other tables you mentioned, but because you understand the physics of how your table is supposed to work, you are able to make it sound considerably good.
I am just making a guess here- I don't know if any great high complience cartridges cartridges are being made that are going to compete with a similarly priced low complience cartridge with an apropriate arm, in that price range. I do know that with older tt's and low priced high complience cartridges, apprpriately set up, the results are laughably good considering what one can obtain them for.
I have tried low complience cart's on lightwieght arms, (the frog was one) and it just didn't work. Sure, it can sound ok, but you are right to question that route, as low complient cart's on that arm would be a waste of money.
I think that another appropriate question would be, is it possible for a high complience cartridge on a lightwieght arm to perform as well or close to a low complience cartridge on a heavier, stiffer arm, considering the technology you can buy in that price range.
I would say, good advice would be, be prepared to replace the arm. Since you are wise enough to search for a cart that is of the specs you are looking for, it seems wise to consider what arms you would be willing to buy in addition, to go with your new cart.

Sdecker, congratulations on your uprade.
The conditions you describe as well as the sound definitely indicate to me that you are suffering from not enough mass with your tonearm. I tried to find a picture of your arm but was unsuccessful, but perhaps I can share some tweaks with you that I have used in the past, but first, I'll try to explain your objective(s).
The complience is of corse, the stiffness of the suspension of the cartridge. You can substitute 'weight' for mass for concerns of the arm. The 'weight', if you will, affects the inertia of the arm, as it resist movement.
Every combination of complience and mass produces a resonent frequency that is the natural resonence of that combination. If it falls in the audioband, every time that frequency is produced it will vibrate in sympathy. The result in the range here is masking of those particular frequencies. You want to make the arm heavy enough to drop that frequency out of the audioband.
You can do it by adding weight right at the cartridge. As you move back toward the pivot, you will have to add more weight to equal the inertia of weight added at the headshell. Also, the more weight you add at the headshell, the more weight you need for counterweight.
electrical tape is a good substitute for armwrap. You can wrap it around like some commercailly avaivable do, or you can run strips straight with the tube. If you put it on without tension, or too much tension, it will stay put. This will help damp the arm from ringing.
You could also stuff the armtube. I have used a drinking straw and cotton on both the audioquest and immedia with good results. The straw is to isolate the wire from being smashed against the armtube and/or stuffing, which could be an undesireable dialectric for the wire. You could do variations, I have found cotton to work the best. Many tonearms just use packing foam, you could try that without a straw.
If your arm has a separate tailpiece (the part the counterweight slides on) it may be hollow. If it is hollow, you could stuff that.
If you can get a hold of some lead sheathing, with is available from some commercail construction suppliers, that could be used for a variety of things. it can be cut to any size, and is less than 1/16" thick, and quite heavy and flexable. I have the counterweight of my rega wrapped with it, so it is half lead. It is just taped tightly on, and it works well.
If you go to the hardware store, you could find some collers that have an allen screw in them, sort of like the fancy counterwieghts for rega's, just not as heavy, but this would be a cheap, fast way of increasing the couterwieght. Find them at ace.
I hope at least some of these help. It sounds like you already got into the thread of twl's tonearm tweak, "strange tonearm treak long". If you get your resonence down closer to where you want it, you could try some variations on some of the different explanations of why it works so well. If you were to to some similar or separete variations of twl's tweak on your arm, you could not only possibly improve your arm but help in explaining or proving the theories behind it.