krell ksa100 vs. audio research 150.2

The ARC 150.2 is a very good, excellent sounding solid state amp and works very well with the Vandys (no need to worry about tubes with it). It's comparatively small and runs cool; a very underrated performer, along with the 100.2, in my opinion. The Krell is a pure Class A amp, meaning that it draws constant current out of your wall and runs VERY hot--it will heat up a room very quickly. It is a very well-designed and extremely powerful amp and very clean sounding, with great bass control, but keep in mind that it is older (last made in the early 80s), and were you to get one used you might have to replace the caps in it (if not already done), and the cooling fan in the early KSAs was a slight trouble spot (one reason why they went to the big heat sinks on the KSA 80 and 200 models that followed it). Much as I like the old Krells (I owned both a KSA 50Mk II and a KSA 80 in my solid state days), given your budgetary constraints the ARC might be a better choice. Either of these amps is a step up in resolution and overall performance from your NAD preamp, which is a very nice unit but not quite in the same league as the amps you're considering, so at some point down the road you might also consider replacing it (though it should work fine with the amps in question for now, particularly if your source is satellite radio).