Are you not happy with the sound of the UM2 straight out of your PS3?
I have the Little Dot I+ Hybrid amp with stock tubes, which I have hooked up to the Nuforce uDac. I'm listening to this combination right now with my UM3X. I'm trying it out as I just got the UM3X today and I haven't had the I+ for long (I brought it to get a taste of tubes) - neither are burned in yet. I plan to run the UM3X off the Meier Audio CORA STEPDANCE when it arrives.
At this point in time I'm not blown away by the I+. It's added a degree of smoothness, reduced treble harshness (not that I've found the UM3X to have harsh treble) but these are very subtle changes. I'm just as happy listening straight out of the uDac, which possibly provides a little extra detail in fact. It is recommended that the stock tubes in the I+ are replaced though as they're not highly regarded.
As such, for your scenario I'm not sure I'd bother with the I+, in fact, as per stang's response, I probably wouldn't bother introducing an amp into the mix at all. The UM2 are not hard to drive after all.
However, I would highly recommend the uDac to compliment your laptop listening. I was very impressed by the difference over the on-board sound from my PC; there was a significant increase in detail and seperation, to list just a couple of the improvements. I'm sure you know this, but if you do invest in a dedicated DAC, I recommend using only CD quality audio and above (i.e. not low bit rate mp3) to get the full benefit.