The Adcom GFA 535 is still my top choice but even for it's small size, it's still too big on the table with all the other gear. I came across the Furman SP20AB in my searches and everything seems right. Size, XLR ins, volume control, 20w @ 4ohms. Only thing is I can't seem to find any real info on this thing, just the Furman's print copied on every site. Can't even tell if it's a class D amp which it may be.
If you want something small with high output for it size then take a look at this: