The KBT Race would only be 1/4in smaller or so. The key layout is similar, just a thinner frame.
A Pure, Poker or HHKB is the only way to get much smaller and even then, you are really only talking one row of keys in height and width from what you have.
For Cherry, I wouldn't get blue if you are concerned with noise, in fact I would recommend red or black and lube it, that will make it more quiet. There is no way to be as silent as a rubber dome, there is just too many mechanical parts moving around. However a lubed, linear can be pretty quiet. My lubed red, Race is close to a dome, but under a lot of typing it's obvious it isn't (a bit of foam underneath the board might help a bit more). If you do go with KBT, don't get backlit (especially white, I think the keys are just painted). The PBT's feel great, but the font will wipe off soon as it's only printed on. The case paint will also wear off fast if you get white, in other words, you want a non-backlit, black.
As for quality, the HHKB will best the rest, but you will pay dearly for it. It will also possibly be much quieter as it's not a Cherry switch but instead a modified rubber dome.
Another Cherry option is a GH60 or Poker (both are the same size as a Pure, GH60 can even use a Pure case). Neither is easy to find, and the GH60 is only now gearing up for actual sale but won't be as expensive as a Poker, but you will have to assemble it yourself.
If you want high quality, quiet and now, your best bet is an HHKB, but like I said, it won't be cheap.
If you can wait, a GH60 could be your best bet.
If you want it cheap and now, keeping what you have, or a Pure is probably the best bet.
Edit: Jabar got some of it while I was typing
