I recently picked up a Blackheart BH1H Killer Ant head. Well under 1 watt (uses 2 12AX7s, one preamp one power, so probably around 0.25watts). May not sound much, but remember, a 5W amp is only half as loud as a 50W if run into the same speaker.

An SG starts to overdrive it well at 3 out of 10, and by 5/10 it's actually pretty loud (too loud for home playing), above that it  doesn't get much louder but very distorted - and the design means you're getting power amp distorition, not pre-amp so none of the pre-amp buzzy-ness.

Running into a single 10" Greenback in a closed cab it's very convincing Marshall substitute indeed.

Dave.... can you really ever truly have "too much" when it comes to guitar cabinets? 


On a serious note, Yeah, the Marshall cabs look and sound good, but in the studio, and especially in residential home based studios, a nice small single speaker cab might be the answer. 


When you have to turn something up to get it to sound good....and Marshall's are designed to run loud and sound good..... that might not work well with neighbors, kids, and the wife. 


I had a Marshall Cab that I also picked up for a very good price, but here in the studio, it was more of a dust collector and always in the way, so I sold it.  I hated doing that but I don't play live and it was not being used.