[font=trebuchet ms]In my opinion, Marshalls are a one-trick pony. If you like 'the Marshall sound' it's best to go to the source for it, but there's nothing else in there. So yeah, for blues rock, you need something else.
Fender amps have long been associated with some of the best players and most recognisable riffs. Another one-trick pony, perhaps, but it's a really good pony.
My personal tastes favour 70's Ampeg V-series amps. I have a '76 VT-22 (120 Watt, 2x12" open-back combo) that I rarely play anymore because it's just too loud for most rooms. I keep it because it has the richest, most 'real' clean sound I've ever known. And when I have enough room to push it into overdrive, it sounds like the voice of God! The V-4 is a head-only version of this amp. The V-4B is the bass head, which is [u]identical[/u] except that it doesn't have reverb.
My everyday amp is a '77 VT-40 that I bought as a flood-damaged salvage job. In stock form, it's a 60 Watt 4x10" open-back combo. The Rolling Stones used these for a lot of their stuff. The head-only version is the V-2. These amps are also seriously loud, but the 1977 model has a master volume control that allows it to sound good without melting the first four rows of the audience. The only part I was able to save from mine was the guts of the amp itself. I couldn't afford four 10" speakers, so I built a 1x15" sealed cab with one WeberVST Ceramic California in it. The speaker is very efficient - when it's cranked, the SPL just as high as the VT-22!
Anyway, you're looking for good blues rock sound. If you can find one of these old beasts, you need look no further. The tone controls offer such a wide variety of great sounds that you don't need to worry about falling into a rut where everything you do sounds the same.
And if you can't find or afford an old Ampeg, check out some of the newer gear from Fender, like the Blues Junior, the Hot Rod DeVille, or some of the re-issues.
Something not as widely known, but every bit as satisfying, is the newly-revived Traynor line of amps from Yorkville Sound. These babies kick ass and take names!
I would strongly recommend staying with tube amps. Unless you're heading into highly-processed/effected teritory, transistor amps aren't quite 'there' yet. They're getting better all the time, but if you want your music to be about just you and your guitar, tubes still rule.[/font]
