HI-FI NEWBIE NEEDS HELP!

I am new to the higher end of music listening, actually I haven’t started the listening part yet. I have just purchased an Emotiva XSP-1 pre and a pair of Magnepan 1.7i’s. My listening room is 14x14 but one wall is not closed off completely and there is an additional open space connected that is 8x9. My budget has been unexpectedly diminished more by having to buy new connectors and speakers cables. I just assumed I would be able to use my old RCA connectors and my 50’ spool of speaker wire I bought from Radio Shack 25 years ago. I will pause while you laugh....Anyway, the jist of it is is that I’ve got $2500 left for an amp. I need advice on what would be good for my setup? What would last the next 25 years, as I am a poor man with expensive tastes and will probably not be able to make any further upgrades. Would something used and older be out of date technically in 10-15 years? Could I consider something new that would be adequate for that price point? Should I go mono or two channel? Thank you for your consideration and reply.