Some find them muddy. Others don't. I don't consider my Nomad to be particularly muddy, at least not channels 1 and 3. IMO, channel 2 has far too much bass to use the gain it has on tap, and consequently, I don't use channel 2 much as I'd like to. Some consider the Nomad to have too much mids. Admittedly the mids do sound kinda nasty outside of a band context. However, I've found that in a band context, those excess mids are absolutely indispensable when dealing with another guitarist who refuses to not max out the mid control on his Marshal or Engl. Admittedly, the mids can sound kinda weird, but I've found this to be more the case with 6L6s vs EL34s. With EL34s, the mids do just fine when competing for bandwidth against a Marshal or Engl, but the cleans on channel 1 suffer a bit IMO. The Graphic EQ is indeed very useful for pulling the mids back when they're too much, but it's also great when you want to boost the mids even further and stomp that annoying marshal out of the mix so your leads can be heard for once.
Channel 1's circuit is somewhat similar to the preamp circuit found in blackface and silverrface reverb fender amps. I say somewhat, as there are a few changes that make it not the classic fender reverb preamp. You aren't going to get perfect Fender cleans out of channel 1, but IMO, the cleans to be had are still nice and useful.
Channel 2's circuit looks a lot like a One-wire-mod Marshall 1959 to me. Lots of bass, but as I said before, too much for me. It can do fine for lead work, but forget about tight chugga chugga rhythms. But since you're looking to play blues and rock, you may be able to find useful sounds here.
Channel 3 is kinda similar, but brighter, tighter and faster feeling, with less bass. This channel *is* useful for tight rhythms, but not to Recto levels of gain. Like a JCM800, it only has 3 gain stages to the Recto's 4. Hard (and not so hard) rock? Yes. Modern metal? I haven't tried to take my Nomad that far, but I suspect not.
The Modern/Vintage switches on channels 2 and 3 are subtle. They switch in a resistor that darkens and attenuates output from the preamp and change the reverb mix/return routing. The make the channels a bit quieter and darker, but don't really change the gain structure (unless you've got the channel master volumes up so high you're over driving the FX loop too). On Channel 1, the Normal/Pushed switch is much more useful, IMO. The tonestack get's re-voiced slightly and the resistors between the 2nd and 3rd stage of the preamp that keep the preamp clean get bypassed and allow channel 1 to overdrive under it's own power without any assistance from a pedal. There's very nice crunch sounds to be had in this mode.
