I'd partner the A18 with an Arcam CD player and Monitor Audio speakers. Try both BR2s and RS1s. I'd also try the B&W 685s and the Quad 11Ls.
Any reason why you've focused on the A18? Its certainly worth an audition but I'd try a few different amps around that price point if I were you. I've just been through the whole process (including trying the A18 and CD17) before investing in my wonderful new Denon/MA set-up and there are so many different sounds available at this price point that a bit of wider auditioning is vital to ensure you really like what you get.
A CD192 would go well as would a Rega Apollo. Great speakers if you don't want to upgrade to baimping later would be AVI Neutrons, I heard model IV and they were excellent, John Duncan has the V and says they are good too. Otherwise the B&W685 will be good especially if you like Dance music.
Don't get the CD17, it's rubbish IMO. A rare miss for arcam. Totem Model 1 Sigs, MA GS10's and Dali Ikon 6's all sound excellent with that amp from experience.
Jits:
Am a newbie and trying to match the Arcam A18 Amp with a good quality CD player (under £500) and speakers (Bookshelf).
Any advice on on this would be great.
Thanks
Epos M5/12 ... add MJ Acoustics Pro 50 ... DAC (CA example) ... Airport Express and then use laptop/dvd player as source. Also consider Rega R3, floorstanders with a very small footprint.