Do you like/enjoy the Arcam sound? As in have you compared Arcam amps to NAD, Rotel, Cyrus, Marantz, Roksan etc...
If you do like the Arcam sound then the possibilities are a plenty to upgrade.
For a simple and straight forward upgrade with a noticable difference in sound (clarity, punch as well as power) you could look to upgrade to either the Arcam Alpha 9 integrated and 9P power amp or the same with the Arcam Alpha 10 integrated and 10P power amp.
Another question would be what CD player do you have and what music do you listen to? Also; what speakers are you running?
Another possibility would be to upgrade to the Arcam DiVA range. The A85 integrated and P85 power amps are very good. There are some great deals on the Arcam FMJ A32 amps on Ebay currently. Brand new and at a very VERY good price for a stunning amp - http://www.arcam.co.uk/prod_fmj_A32_intro.cfm