there are some really good "clean" boosts you could do.
ZVex Super Hard On
Catalinbread Sagrado Poblano Picoso
EHX LPB-1
i've used the LPB-1 as an add-on to a pedal that i added a tonestack to, and use catalinbread as a separate effect. the catalinbread adds a little midrange and tubeyness to my ears, while the LPB-1 you can't even tell its in the circuit. i haven't built the SHO, but i've heard nothing but good things, and its super small.