I bought a V3MC not too long ago. I did not opt for the V30 as those are probably imports from China and not the good ones from the UK. Yes, the V3M does need some tube changes. I found it rather harsh at first. Discovered the EL84 bias was not correct and put it where it should be and all was good. Still the two lead channels did nothing but feedback. I was not ready to give up so I replaced all of the preamp tubes. Trick to this amp is V2, that needs to be a 12AT7 if you want good base response and adjustable gain. Now the V3MC can recreate some vintage tones and still crank out some heavy tones for metal. Also replaced the speaker with one that was not as efficient. Since I bought a WGS Black Hawk HP100 for my Mark IV, somehow I believe the Mark IV was a bit too much for the WGS speaker (kept heating up the voice coil). Actually there is nothing wrong with the Carvin GT12 speaker, sounded great in my extension cab and the Mark IV. The WGS BH HP100 is now in the V3MC. This little amp works great, sounds decent. Only issue I can see is the acoustic cavity of the amp is too small for a 12 inch speaker. I ran the amp through a 412 with V30's (Mesa originals that I mounted in an Egnator cab) and it rocks. Also plugged it into my extension 1x12 cab and used the on board speaker in parallel, competes with the Mark IV very well. I basically bought this amp for travel since the Mark IV is too heavy to carry and too loud for practice at my friends house. Why we do it after all the kids are put to bed I am not sure (oh wait, never mind, when they are up all they do is interfere with their dad, pull the chords out, turn off the amp, and just mess with him for attention).
My first impressions, should I send it back? after tweaking the amp, heck no, its a keeper! I was considering a TA-30 but for the price the V3MC is a great amp with the proper preamp tubes (and correct bias set for the EL84). Quality wise, not bad, (Mesa would be better quality, at least my MKV, MKIV, RA100 and the old MKIII are top notch). I would prefer toggle switches for power selector or output impedance than the slide switches (must be made from CSW since they have the same feel (open frame slide switch are okay but do not have precise detents and feel loose, believe it or not, they are not cheap switches and have used them in the past and now at a new company we use them as well). The clean channel is nice and has a few voicing switches as do the other two lead channels. However, effects of the different settings are more appreciated with an extension cab or 412 than through the combo speaker due to signal cancellation. The power cord seems a little thin so I am using the old one from my Mark IV (I replaced it with a longer one). Foot switch works well, boost also is a great feature. Effects loop is also great. The digital reverb is also nice (be weary of EBAY as some of the early production units had some feedback issues which caused a motor boat sound, I can dial this in with all of my digital delays if feedback is set too high, also called decay). The cabinet of the V3MC is made from multi layer plywood. I did have some vibration between the metal cover plate and grill plate. I was able to fix that with rubber sealing tape to dampen the sheet metal vibration. This occurred after I removed the amp from the enclosure to check tube bias. Overall, not a bad amp to have.
There are probably other amps that are just as good or better, but I chose this for the 3 channels, overall weight and final cost.