I have heard the latest D225 stereo amp compared to the Samson mono's. As good as the D225 is, trust me when I say the Samsons are a step forward. The main reason is the new power supply. Also, each mono amp has the same sized transformer as used in the one stereo amp. There is also more room to work inside the monos making for better layout etc.
I did not hear the SE version of the Nuforce amps, but it seems Ecruz thinks even the D225 amp surpassed it. My old ST225 integrated TRL amp bested the combination of Canary CA339 monoblock tube amps ($14,000) and a fully loaded Audio Horizons 2.1 tube preamp ($3200). My old ST225 integrated is not nearly as good as the Samson and Dude!
I wish I had tried the Nuforce SE's so I could have more first hand experience with those amps.