Tubes would be a good direction to go if you are seeking warmth. I took from your post and your components that you were looking for SS, but in re-reading it I may have been wrong. I'd sell the Marantz and go with a tubed integrated, as has already been suggested. I'd be looking at Cayin, PrimaLuna, Jolida 502 or 302, etc., to warm things up in your price range. I would guess that if you used the Marantz (solid state) pre section that you may be running into more of the same harshness. The pre section is very important and should not be taken lightly. So the short answer is I don't think adding a power amp will do what you are after in eliminating the perceived harshness. Personally I've found that a preamp can potentially have greater effect in that regard - if you could add something to warm it up adding a warm pre would have more impact in my experience, but I don't think you can do that with your Marrantz receiver. I also wonder if the harshness you are describing has to do with "warmth", which I take to be an emphasis of the low-midrange, as opposed to clipping and distortion(s). Regardless, I'd still say tubes would be a great way to go. If you are looking for "warmer" sounding SS power amps in that price range, besides the Aleph recommendation, I'd second the Odyssey knod, and would also suggest a vintage Bedini 25/25 or 10/10 if your speakers are efficient enough (there are certainly risks in buying vintage stuff of that age though so weigh that in your considerations). The Aleph and Bedini run in Class A and are best left on 24/7 so can become space-heaters - great if you live in a cold climate, not so much fun in the South. Again, I'd still say your weak link will remain your pre in that case.
