Take a look at the review of the xpa 5 in Stereophile. There is a link on the Emotiva web page for the amp. It was written by Kal Rubinson. He is a good reviewer and not prone to heap praise on everything he reviews. He compares it to a Bryston, which is a nice amp. I think it is also a Stereophile "B" Recommended Product. Emotiva has a forum on their site. Also search here for comments. Emotiva gets a lot of praise. It also has free shipping and a 30 day return policy, although I am not sure how much the shipping costs end up being if you ship it back. Again, I have no experience with it, but it does seem to be pretty popular.
Pretty much any of the amps you are looking at will do a brief 3 ohm. Look at the power rating at 4 ohm versus 8 ohm for an idea of their ability to go low. Ideally they should "double down" which means their rating is twice at much at 4 ohm as at 8 ohm. Most amps in this price range will not do that but it does give an idea of power reserve.
The Emotiva amps have high gain, something like 31 dB, which may be a problem if you pre-amp also has high gain.
Pretty much any of the amps you are looking at will do a brief 3 ohm. Look at the power rating at 4 ohm versus 8 ohm for an idea of their ability to go low. Ideally they should "double down" which means their rating is twice at much at 4 ohm as at 8 ohm. Most amps in this price range will not do that but it does give an idea of power reserve.
The Emotiva amps have high gain, something like 31 dB, which may be a problem if you pre-amp also has high gain.