I've been using an HD500 and DT50 head into a Lopo 2x12 closed back cabinet with V30s for about a year now.  I connect the speaker emulated DI from the DT50 head to the board for FOH.  Overall it sounds pretty great.  I also tried an Avatar 2x12 Contemporary size cab loaded with the Vetta 1 combo speakers.  The Avatar cab with those speakers sounds a little woofy on the low end, but pretty easy to control by using an eq to dial out some of the low frequencies.  I like the Lopo cab with V30s better.

The DT50 has more than enough power for any venue I've played and since I'm only using it as backline stage monitor it is overkill. A significant problem is that the DI is connected to the master volume on the amp.  If I change the volume to adjust my stage sound it changes the FOH feed.  It became a hassle so I decided to try using just a FRFR powered speaker as my monitor. 

I can run from the HD500 to the FRFR speaker and daisy chain from it to the board for FOH.  I use the FRFR speaker volume control for monitor level without affecting the feed level going to FOH. I had to recreate all my patches for FRFR setup and like it very much. 

I also tried a Tech21 Power Engine 60.  It has a different voice than a FRFR speaker, but it also works great.  I use the PE60 as my monitor and connect it to the FRFR speaker setup on a stand to side fill the stage so the rest of my band can hear my guitar better. 

I've done two gigs with this setup and everyone likes it better than the DT50.  The tone through FOH is great and the band is happy.  It looks like I'm going to retire the DT50 and sell it to get another guitar.