Boca, sorry for late reply, but I recently bought the Onkyo and ccompared the 5008 with
* Rotel 1560
* NAD T785
* Marantz 7005
* Cambridge Audio Azur 650
It was a close finish between the Marantz and Onkyo. Both very detailed and musical. The onkyo won on clarity in the high frequencies. Just al little more subtle and precise, but really just a little.
Rotel dropped immediately, missing about everything in musicality you would expect from a ? 2600,- amp. No detail in high frequencies, it dsounded like the tweeters were ciovered with a woolen blanket. At first I thought something in the settings was wrong, but switching to pure audio in stereo gave the same disappointing result.
Cambridge sounded too rough and unsubtle, overpowered and unbalanced. Exit too.
NAD had severe problems on controlling the bass, it was pretty awful. Totally unexpected, a 3K amp would do a better job IMHO.
Marantz was very musical, open and live. Yet the onkyo won on slight details in clarity. the price tag difference was an issue (Marantz way cheaper then Onkyo) but in the end I chose quality over price.
Arcam was not available, but the AVR600 where I would go for is a totally different deal anyway when it comes to budget. AVR 400 may have done the trick but it is not available here (yet). As the AVR 400 will be available in the UK it would be a nice comparison for the OP to compare the amps.