Please igniore Drummerman... He has a dislike to Arcam and Monitor Audio and alot of other 'more common makes'... Haha
With regards to the Arcam A90, i'd leave well alone. I feel that although it has power in abundance, its hollow sounding and lacks in bass weight and midrange smoothness. The What hifi review has it down to a tee.
The Arcam FMJ A32 is a superb amp and really shows its class compared to the A90. Bags of power, sublime bass weight which is well controlled with great midrange and crisp/clear treble.
I'd defiintly consider partnering that with the Arcam CD192 or the CD92. Both superb CDP's.
With regards to other amps you coulc consider the Roksan Kandy LIII integrated or the Cyrus 8v2 amp. Both would go well with the Arcam CDPs as well as the Cyrus 8 CDP and the Rega Apollo CDP.
As for speakers i would heartyly recemmend the Monitor Audio RS6's the RS8s and the GS20's. Also worth considering would be the B&W 683's, B&W CM7's, B&W 704's and the B&W 705's.
Depends on your budget but i feel that if your going for the pricey Arcam separates, you'd be better off spending more than £500 on speakers. Out of the above, i'd definitly go for the B&W CM7s, the M/A RS6's and the M/A GS20's.