software

I'm looking for a quality, tube bass head, and these are the two that seem the most interesting to me (I'm leaning towards the Boogie). Does anyone have experience with either one?

Both will knock the building down. The Mesa is much pickier about its EQ. It can take time to get right. That said, it's nowhere near as picky as the M2000. The Ampeg is more of a plug and play amp. When paired with an 8x10, it's THE rock sound. I think you'll find the Mesa to be more versatile for sure. I don't know how gritty the 400 will get at high volumes though.

I have a Mesa Walkabout. It's part of the Mpulse line. SS power, parametric EQs, fancy stuff, and tube preamps. Once you get em dialed in, they're great. The others in that line are the 360, the 600, and the 750. Little secret about the Walkabout - its rated 300W @ 4 ohms, but if you ask Mesa, they'll say it works with 2. I run mine at 2 ohms all day long with no problems - and a free extra 300W.

Just throwing out a couple more options for ya.