For 300 to 400 you can jam some nice caps in the critical spots and do some diodes, with fuse, new power cable, very easily
Probably can do it well under 200 if you are able to do it pretty easily yourself for sure, somebody might mod it for you with shipping for around 300 as well. I can tell you I had a LS7 I believe which was the tube based hybrid? And I had a LS3. The 7 was nice, I remember it being a little dry, maybe a bit thin depending on the amp and speaker match you run
Definitely you could get better midrange bloom and BAss down low with some higher grade caps, I suggest the new Clarity ESA range which are very dynamic and warm, far better prices and sound over the big mundorfs etc
Clarity MR range could be even better, but very expensive, and get much larger in size. If you can make them fit, but remember they become far larger when you go to exotic caps over most manufacture stock sizes at an equal value. Jantzen Superior caps are great as well for very little money, better than the Relcaps, MIT, cardas, mundorf ranges for sure at the price levels.
That unit should have a ton of room in the AR chassis and I think its capacitor configuration is pretty simple and not many of them. If you want the most bang for the buck and can do it with a little good soldering thats where I would start for the most effective mod, all the rest will fall behind for fun.