Belles 150A or keep current amp

I use Vandersteen 2ce speakers with an old Krell KST 100 amp, YBA 2 preamp in a 10 x 12 room, modest volumes (85db nominal, 95 db peaks) playing mostly jazz. I received the amp with all cap replacements for free from a cousin. I've heard better but is it worth it to drop $1K - 1.5K on an amp,say a Belles?