I listened to both and bought the Nuforce. Don't be tempted by early second hand ones though - problematic for RFI and were released to production too early. If buying second hand, make sure you buy the V2 version which now very well sorted (V2 is marked on the fascia) if that's the direction you take. The US ones can be used in the UK without modification so if you're thinking of a trip, you could save yourself some money.
Also have a look at these;Trichord which have some advantages over the ones you mention; you can plug a subwoofer in to the speaker sockets of this one without breaking the sub and it has a more conventional power supply. Had these been available when I bought, they would certainly have been on the shortlist.
Valve preamps are very popular with these. I use a Promitheus CVT though which is perfect for the Nuforce.
I think you'd probably be happy with any of these. They're very clear with a good bass and particularly good with difficult speakers.
On the debit side, these tend to be quite a 'polite' sounding class of amp which generally only do imaging moderately well compared to the best transistorized or valve amps.
