I'll say upfront that I'm no amp expert, but I'd like to share an excerpt from an e-mail response that I got from Outlaw Audio. This particular section was addressing their amps versus the Emotiva MPS-1:
"In addition, our multi-channel amplifiers utilize a partial monoblock design. This means that each amp channel is separate from the next. However, unlike a full monoblock design, each of our amp modules share a common power supply. The benefit of this approach is readily apparent in real world applications. When just one or two channels in a particular movie or music soundtrack requires a sudden but continued, high level output, the loaded channels will draw additional current from the shared transformers (this is not possible in a monoblock design as each module is limited to the output that its transformer can deliver)."
IMO, it comes down to how the amp is designed, not whether or not it has independent or shared power supplies. Either design can be good or bad.
As for internet-only companies, I tried two this year: SVS and Emotiva. There are pluses and minuses. Customer service has been pretty good, although e-mail responses from Emotiva (if I even get one) have taken days. They are better on the phone, but I don't always have time for that during their business hours. SVS e-mail responses have always been within a day, including nights and weekends. My first amp from Emotiva was a dud, but they shipped me out a new one and provided a pre-paid return label for the first one, so that all worked out fine. My first sub from SVS was damaged in shipping, but they also shipped out a new one and gave me a pre-paid label for the first one. A benefit is generally lower cost for performance versus big name brands and regular stores, and a disadvantage is the hassle of dealing with shipping (having to be home when it arrives and/or dealing with shipping it back). I don't regret buying from them. The Emotiva amp is good, and the SVS sub sounds great. I'm still waiting on a replacement amp for my sub (the original design has a flaw), but that's supposed to arrive within about a month. As a frame of reference for me, when I bought a defective sub from a local audio dealer, they lied to me for two years and said that it was fine until I got the manufacturer involved...SVS and Emotiva never gave me any grief at all when it came to fixing a problem.