Id say the 2 main contenders are singxer sa1 and schiit jotunheim2.
Jot2 - its a warm amp, adding extra low end and warmth. Pretty great power for planars and decent resolving capabilities with a small-ish stage. Has a tiny bit of upper treble harshness but its pretty minimal.
sa1 - very mid-centric amp. Its got creamy and sensual mids, how ever, everything else suffers in some way from it. The highs are a bit recessed and the lower end doesnt have the same umph to it as jot2. Stage is also pretty small, how ever, if you want stage, youre well in to 4 figures for an amp
Sa1 also struggles with more demanding planars, more so then jot2.
Its also borderline required for you, or the prev. owner to mod the sa1. Theres a shunt mod that makes it sounds noticably better. with out the mod, jot2 takes the easy W.