HELP Why no bass? Why bright?

It could be anything, but I wouldn't even think about doing any critical listening until you break the new pieces in for a few hundred hours. They're going to change. Wait and see if you like the way they sound after break-in.

B&W makes bright speakers, the arcam 65 is a bit laid back and was probably covering up for them. I think you have the right idea on the bass being more controlled or perhaps the brightness is just distracting you. I'd switch to speakers that match your amp or change amps again, I guess you found a bad combo. If you want to mess with the decor you could try room treatments, but don't expect much from break in. It's just a scam to keep you from returing an item while you still can. Electronical components don't have moving parts so they can't really 'break in', some amps are known to 'warm up' which makes sense since heat affects conductivity, but how this affects sound is beyond me. If it sounds bad now, it will probably sound bad later on.

Sydney- My experiences, as Phild stated, have proved to me the necessity to allow components to "break-in". With all due respect to Perk, all of the vendor spec sheets that I've seen indicate that component drift or variation occurs more profoundly during the initial and then again near the end-of-life operation periods. Most of this is due to thermal effects, both steadystate and cyclic. Last I looked, electronic components were composed of quite a few resistors and capacitors, and tubes and/or transistors. I agree that if a component is "bad", that time will rarely repair it for you. However, the sound attributed to components does and will change over time, and predominately during the initial use period.
As for your system, was the integrated the only piece that you changed(are the ICs and/or speaker cable new?)? After the amp has been used for at least a week, you can then determine if you need to consider speaker placement tweaking (toe-in/tilt), some room treatment, or possibly try other wires to help shift the tonal balance to more of your liking. Take your time, and enjoy.