I had an HCA 1500 with my RM1s and it was underpowered. I haven't heard the 1080. I recently went from a biamp setup--Counterpoint NP-100 on the top, QSC PLX1202 on the bottom--to a single amplifier, the McCormack DNA-225. I picked it up for $1700, a bit over your budget, but it is a very, very nice amplifier, with more than enough grunt to get the RM1s up and going.
John K.