From the spec, they should be very easy to drive and match well with most of the amps. They just sound thiner than what we would like. Also, the lower frequency is just not there. Lack of clarity and no punch. You would wonder where is the bass as it claims 38 Hz vs 55 Hz of ATC. Again, these are just our opinions so you can choose whatever you prefer.
Needless to say, this has not been my experience at all with the SR17's and I've owned two different pairs (one of the earlier models, and currently a recent one). Nothing in your description of them resembles my impressions of them so I imagine it may be a matter of synergy. Either that, or your friend did not allow them to break in long enough as, by all accounts, they do have a long break-in period. I've used them with about five different amps, both tubes and SS. I did experience some lack of low end using the Pass Labs Aleph 5 with them, but I do think that was a drawback of that particular amp. My favorites have seemed to bring more muscle to the task: Mesa Baron and currently a Portal Panache. In spite of having heard more than once that the SR17's are voiced for tubes, I have not found that I like them as much with the lower powered tube amps I've tried them with, but they were still great performers here...just better with more power behind them IMO. Those amps were Quicksilver Mini-Mites, Quicksilver EL34 Triode Prototypes, and a revamped Scott 299C (going from 35W to 17W respectively). I'm pretty sure I've read all the online reviews and comments on Internet forums on these monitors and absolutely none reflect the same experience you and your friend had, so I'd have to guess something was amiss there. Regardless, I'll definitely look to check out those ATC's sometime...sounds like a worthy candidate!
Marco