Unfortunately very few of us have played the 50 -- so most everyone is going to recommend the 30 -- especially Les, as it's one of his favourites..
Dusty's right, I haven't played the DG50, though I plan on getting one at some point and adding it to my little PRS amp arsenal. So I'm absolutely not qualified to compare the two amps.
What I can do is share info on the DG30. But before I do, I can recommend that you take a listen to Grissom's latest record,
How It Feels To Fly. The 30 is all over that record, and the amp does what it does on that record, effortlessly. You can just take some quick listens on iTunes if you don't want to buy the whole thing. The reason I recommend doing this is so that you get a clear picture of what the amp was
designed to do live and in the studio.
Though it is a versatile, pro level amp in every way, if you need high headroom, this is not your amp. What it gives you instead is the sweet, smooth gradual breakup that many amps promise but can't deliver.
Will it do beautiful cleans? Yes, absolutely, depending on the relative settings of the gain, master, and most importantly, your guitar's volume knob. Here's a clip of mine with a PRS 408, you'll hear differences as i play with the volume knob, and controls on the guitar. Toward the end I use it with some delay and modulation.
https://soundcloud.com/lschefman/dg-demo-track
There are a bunch of other short clips on my little Soundcloud site of the amp to demo various things. And the demo videos by Grissom on the PRS Product website are very accurate representations of what the thing sounds like.
I think the amp would be ideal for your music and guitar, but only if you can live with the fact that it's designed to break up rather quickly. If you're just not a guy who's going to put that guitar volume knob to use, I'd recommend one of the two-channel amps PRS builds. They truly sound superb, and have especially nice cleans.
Finally, if you decide the DG might be for you, it's an amp that requires a little bit of learning to dial in. The time spent doing that is worth it, but it's not a "set it and forget it" amp. The controls are very interactive, and are designed to be interactive with your guitar.