Overdose said:
Firstly, unless there is a fundamental problem with one of your amplifiers, changing them is unlikely to make the large difference that you appear to need.
Forget modding.
As suggested, check all wiring connections and double check, as something simple could well be the issue.
Failing all that, the integrated amp is plenty powerful enough for most hifi speakers, so you might be best to offload the speakers and power amp and then go on the hunt for a pair of speakers that you like.
Edit: I see that you have checked the wiring. Why not get the same system as your friends if it has the sound you are looking for?
If you are determined to simply swap boxes in the hope of getting something you like, this is reasonable advice.
The reality is that you have somehow managed to aquire one of the least involving, least engaging systems produced in the nineties, the Arcam amps are smooth and refined, determined not to offend, for largish speakers the Chesters have little in the way of bass weight or punch and a lack of presence throughout out the rest of the range.
Though that might suit some people it is about as much use playing the kind of rock music that you seem to favour as it is possible to get for the money, it is really no surprise you don't like the results.
There are plenty of people on here that will recommend that you buy all the usual suspects, a Marantz this, Monitor Audio that and all the other mid fi components that are currently flavour of the month.
Dare to be different, go to a dealer and try something that plays your style of music in an engaging way that lifts your spirits, don't worry if it does not conform to conventional wisdom, if it does not contain 5* products that are flavour of the month, buy something that engages you!