Hey, Mark. I've played guitar for... well, forever it seems, and I gotta tell you that the MG series of Marshalls are not really that highly regarded.
If you want to use headphones, keep the cost low, and still get a nice tone, a Tech 21 Trademark 60 is pretty hard to beat. Its solidstate, but dont let that throw you... I used one to record with and it sounds killer for the money, and actually sounds better than a lot of tube amps.
The Tech 21 is stone reliable, sounds great and wont break the bank. IMO, its a great bang for the buck.
Tech 21's site:
Tech 21 - Trademark Series Guitar Amps
Currently on Ebay:
tech 21 trademark 60, great deals on Musical Instruments on eBay!
Harmony Central reviews:
Tech 21 Trademark 60: Harmony Central User Reviews
BTW, A great source of information for everything guitars and amps is the MetroAmp.com, and the forum there. I've been a member of the MetroAmp forum for a while, and made a lot of friends there. TONS of valuable info, and a great bunch of guys... just like here!!
MetroAmp:
Metropoulos Amplification - The best vintage Marshall plexi replicas in the world.
MetroAmp Forum:
MetroAmp.com Forum • Index page
Check it out, and post what you decide amp wise!!