Congratulations, those customs look gorgeous, I hope they sound as good as they look. I rarely listen to my customs, or universals, without an amp. I recommend a Leckerton amp, for the price its a great buy.
I use amps with customs all the time. No tube amps, though. IEMs (generally, not customs specifically) tend to be more sensitive than full-size headphones, and pick up low-level amp noise very easily. Most tube amps tend to be a little noisy, although (on good amps, anyway) not noticeable on full-sized phones. This doesn't rule out all tube amps, but read reviews of them carefully to confirm they're noiseless, or that the noise level is low enough to not be distracting on IEMs.