to answer the OP's question rather than get in to the watt debate...heh
the IQ5's can thrive on better amplification than what you are currently giving them...the Denon is a fine AV amp, but can happily be beaten in stereo by most £200 stereo amps....and with IQ5's spending more can yield better results.....likewise feeding them a decent CD player rather than from a DVD player (i assume thats what you are doing?)
If you have a total budget of around £400-500, look at Cambridge Audio, NAD and Marantz and good potential partners for amp and CD players together...or if you can go higher, consider makes such as entry level Arcam..
or if you dont mind going second hand then you got Arcam, Musical Fidelity, Cyrus, plus many more worth considering....
with amps, altho a high wattage should mean its capable of powering the speakers effectively, this isnt always the case, they need a good solid power supply as well, otherwise the amp will be drawing more than the PS can give which will fail the amp as well......so high watts is good, but a heavy box usually means a nice chunky power supply...heh...so give it a lift, if you struggle then it shouldnt be bad...(still no guarantee tho, but a good indicator)