Just want to clarify, the "era of weird mids" is 2007-2012 for QR's. Splawns mid-2012 and after have the "modern" circuit version, just without the newer switching features. Splawn from 2005-2006 have only 3 preamp tubes, crappy clean channels, but AMAZING drive channels - no weird mids there, and there's a reason why the newest Splawns have a switch on them that specifically goes back to the "06" voicing. For the sake of completeness, there was also a version of the QR without gears, and a high/low input like a 2203, from the years 2004-2005 (which I haven't been able to get my hands on... yet).
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To the OP, I would not recommend Splawn for what you are describing. I love my Splawns, a lot, but I really don't think they do an authentic 70's rock sound because they just don't have a certain.. idk. Grit? Rawness? To them. Those sounds you describe are from amps that quite frankly also had a lot of drawbacks, flubby bass, etc... that's why people were modding them and all sorts of stuff - it was a time of experimentation and progress as far as guitar tones are concerned.
On the other hand, I think a Ceriatone King Kong is right up your alley. I have a stock one - no special channel requests etc - and Channel 1 does a very good impression of a late plexi panel super lead, except you are stuck on the high treble channel all the time (no jumpering). Channel 2 with its two gain controls, bright switches, and switchable clipping diodes... it's hard not to give it a glowing review. It'll do a lot of sounds from that era anywhere super lead based, modded or unmodded.
The compromise is that it is a cascading gain stage setup, same as a JMP 2203 or 2204, but it's not going to have that unique growl that a real 2203 has because it's not voiced quite the same way. It's voiced more like a 1987/1959 which is a hair smoother in the mids, but still plenty bright. Add in the various switches and it can get into modern detuned heavy metal if you really want. It's just extremely versatile, but you might spend a lot of time standing in front of it flicking switches - not something you can really do live if you use it for gigging because the Era switch (diodes) has a MASSIVE affect on the volume of the amp. No diodes will blow your ears out, switching in the diodes cuts the volume substantially... would drive the sound guy nuts. So pick the sound you like before you leave home haha, and add a pedal.
As others have said, you can customize the channels somewhat, or make special requests - or if you're handy, they are