For many years I ran my 2.5s with a 12W Cary SE Class A tube amp, and was very, very happy with the result. This was based on a recommendation a long time ago from Arnie, the founder of A-gon, when he still ran a B&M store, Accutronics, in Ann Arbor (so many As...). These days I'd be inclined to look at whatever PrimaLuna amp you can reach with your budget.