PS/2 and USB (HID) keyboards impose maximum bandwidth caps, though I think they're close to ~100wpm+, maybe ~115wpm. I could be wrong. Still, no keyboard will improve speed beyond the PC's (integrated keyboard controller) processing capability.
A shoddy/cheap keyboard might pack slower controller logic (or inefficient debounce methods) and impose further caps. A better/costly keyboard might promise faster typing throughput, but that's much like advertising claims that a particular pair of athletic shoes will let you run and jump 30% faster and higher than before.
Beyond your "comfortable" speed threshold (~90wpm for you, ~75wpm for me) you'll reach a plateau of diminishing returns; constant exercise/practice is necessary to keep the edge on this learned fine motor skill. It's not just about using it more, it's about pushing yourself faster.
[Edit]
You can train yourself on more optimized keyboard layouts. DVORAK is perhaps the "fastest", though I went with COLEMAK (easier for a QWERTY typist to learn). The learning curve for me was about 2-3 months of constant casual practice/use before my COLEMAK speed reached parity with my QWERTY (which now sucks, incidentally); now I type substantially faster than before.
Blank keycaps (or keycaps "marked" with textures) speed the learning curve somewhat. And confuse the hell out of meddling coworkers who cannot make any sense out of unmarked non-QWERTY keyboards, heeheehee.