Hey Border
In response to your PM, I ve never tried the Lemmy, however if it saves you a grand, then it may be a better way to go based on your genre and volume requirements.
Yes the VBA400 will give you more clean headroom, but that might not necessarily be a good thing if you want to push power tubes in OD. If I crank the master on mine, I rarely turn the earlier gain stage past 3 or 4. OTOH, cranking the early gain stage and dropping the master can give a fairly gritty preamp style OD, if you like that sound (I personally prefer power tube saturation so go figure). I bet the Lemmy would sound badass pushed hard. Talk to Mark Olsen here on TB about Marshalls and headrom. He is using an older style superbass/lead amp rated at something like 30W in a full band setting (I think) and as far as I know has no volume problems.
Not sure about reliability issues - my VBA 400 hasnt had probs yet - touching wood right now.
I think either will work for you with you if you want to stay Marshall, however don't rule out other brands (e.g. Mesa. Ampeg) in similar price brackets.
I would try what you can locally first to get an idea of manufacturer diffs and tones.
Good luck, buying a new amp is great fun! Plus if its not your flavour you can always sell it.