Advice on AV Receiver versus Separates

The 7005 is excellent but a little dated. You might consider one of the more recent Denon/Marantz/Onkyo/Integra AVRs for more up-to-date features.

Why bi- amp? All you need is an amp sufficient for your needs.

I thought bi amping would just double the power to the main speakers and improve sonic quality even at low volumes. Is this not right?

No, it does not but, even if it did, why would you not just buy a bigger amp?

Ok. Got it. So what are the benefits of biamping?

IMHO, nothing but that opinion is not shared universally.

My negative comment on biamping is based on the assumption that it will be accomplished in the most common and least effective way: feeding a full-range signal to two amps which are wired to the two pairs of terminals on a speaker with an internal non-active crossover. That is the type of biamping that is offered by AVRs and (most) prepros. It is also to be distinguished from the biamping involved in bass management and, I believe, the OP was not equating the two.

I do acknowledge that biamping using an electronic crossover feeding amplifiers wired to speaker drivers (and what is found in active speakers) has definite benefits. However, the uninformed associate those benefits with the more common biamping described above.