i agree with the people who say the bb preamp.
i have an rc preamp, a hilbourne and a crunchbox myself. i know (from clips) the bb has plexi-type distortion, but at the same time a powerful clean boost (i know this from the specs) and a nice eq (from my rc boost) - it sounds a really useful thing to have in many ways. the crunchbox doesn't do clean boost, but it has that authentic jcm800-y tone and its a great price, it does what it does and it does it well. the hilbourne is a funny one, in certain situations nothing can touch it, and in others i don't really like it... its perfect for what would be considered a high gain tone in the late 1970s, and perhaps early 80s, works best with low-output pickups.
after a-bing my modded sd-1 with my rc boost, i have doubts about modded pedals, i'll probably go boutique only in future if i want another pedal. not sure what this pedal would be at the moment. maybe a BB actually.