Already posted my thoughts on Marshalls but I really don't think their DFX series competes with a low power valve amp, which is all you need for bedroom/practice use and can even be micced up for a gig or rehearsal (maybe even loud enough for a quiet band rehearsal if you go for 10w).
A 30w power rating is pretty meaningless unless you really need the power and
your budget is really quite low. I'd never expect to get a better than average overdrive tone on a DFX, I honestly just don't really like their sound and will always opt for pedal overdrive instead (Big Muff / Crybaby / Boss MegaDistortion, although the latter is ridiculous so I rarely use it).
To me DFX amps' overdrive sound thin and fizzy with poor clarity in the mid and bottom range; they sound overly trebley or if you roll off the treble (again at the expense of clarity) you get this kind of floaty underwater sound. The clean is okay but they kinda lack punch and "viscerality" - they sound stale and dull in comparison to valve. Marshall's higher end all-valve heads and combos can sound fantastic though, if a little generic. They are good all-round amps but sometimes it's hard to get away from that "classic rock" / metal sound. Very satisfying if you want that though.
I rate Peavey solid-state amps better personally. Marshall just seem to cash in on their names with cheap DFX amps sold to an audience that want the Marshall badge and want 30 watts and higher for no justifiable reason ("louder is better", they think). I find the Marshall brand strength tends to blind people to other options, even if they clearly sound better.
I'm somewhat spoiled by the range of valve amps available at Brighton studios and my (all but uselessly loud) vintage amp though, but for me its more the case that something like a DFX spoils the tone of my S2170SE. The input literally clips with a nasty crackly sound seemingly beceause the output from EMG 81/85 is simply too hot for it to handle. I've used other people's DFX15 and 30 for a couple of years. Conversely an excellent amp can beef up a lower end instrument. I've played my Pacifica 112J through a Marshall JCM 800 (or 900, can't remember) a couple of times and that sounded bloody amazing, surprisingly, so it's always worth investing.
You get this wonderful shimmering, full-bodied yet tight sound with a valve amp and the overdrive is unbeatable by solid state amps, generally speaking (although I've never found a solid state that sounds better than a valve amp.. probably because apparently all the higher end amps are all-valve). You get a soaring, highly dynamic sound with fantastic sustain; the clarity really articulates every note you play and brings out the detail (and weaknesses) in your technique.
I don't want to sound like a snob or something but sometimes I feel embarrassed playing through a cheap solid state amp now; I just feel there's something missing I can't add in myself, which is disappointing.
I've never even bought a guitar amp yet, despite having been playing on electric for about 8 years now, as I've spent years trying other amplifiers belonging to other people before committing to spending serious money on one I know I'll love. I've been looking for me own since about 2007.
Personally I'm interested in the Vox Lil' Night Train as a portable tone box, which I can always plug into an extension cabinet for more output:http://www.dv247.com/guitars/vox-lil-ni ... set--78498
Only 2 watts and sounds great from what I've heard on YouTube (and I've tried the standard Night Train - it really is very good). It's more than loud enough for practising at home and again can always be micced up.
Then I might pair that with a Vox AC30 CC1X (Celestion NeoDog Blue speaker is gorgeous but about £180 for the speaker alone) or something similar, I might try some lesser known brands as I'm far from done trying others yet. The problem with the Vox for me is a lack of a switchable overdrive channel and I could really use an FX loop to cut out tone-sucking pedals like Digitech Whammy. Also the cheaper Chinese model more widely available are taking a hit in the valve arena with solid state rectifiers and generally cheaper contruction.
Personally I'd never choose to use a solid state amp anymore, given the choice. Not with such affordable alternatives available. Cheap exported labour has brought the price of valve amps crashing down in the last 3 or so years, so this doesn't even apply only to the upper end of the market anymore.