BTW is it worth getting a clean boost thing instead.
I want my tone to stay the same but have more harmonics and just generally boosted if that is possible?
If you get a proper clean boost pedal and put it in the FX loop you will get more volume. Put it in front of an overdriven amp though, and it will drive the amp harder and result in more gain.
An SD1 wont do this, nor an 808 or ZW because they have a built in overdrive sound that imparts its tonal quality on the amp. However, they do also sound really good, so its a bit of a toss-up.
I had a clean boost and I've had the analogman modded SD1 (which switches into an 808 as well) and they are fairly different beasts. I dug the clean boost, but only into an already driven amp. It resulted in some really fat lead tones.
But on a relatively clean amp, it was no good. I preferred the clean boost into an overdriven Plexi, but the SD1 into a light gain JCM800.