Hi,
I've just joined and saw this topic. I bought a Marshall MB4410 450w combo, in December '07 for £320, as I love the Marshall sound, have used it on around 6 gigs so far and have been disappointed throughout.
Lack of power for one, and the most annoying hum makes it almost unusable when put thru our PA. Weighing in at 53kg I couldn't afford to send it back to shop 200 miles away (they did free postage when I bought it) so shop agreed to let engineer in my local town have a look at it. He's changed a jack socket but still humming and still sounds under-powered, so am now embarking on a long road of exploratory engineering - on a NEW amp.
The shop in Preston were extremely helpful and after a long conversation with one of their salesmen, he confirmed that he has a lot of these amps as the build quality has declined so much due to out-sourcing, that bass players have moved on. He's had a lot of returns, he actually said he's had more Marshalls returned than any other make.
Maybe I've just got a duff one but be warned about the drop in build quality.
My advice would be to test it first
Hope it helps
Ian Mac