Nicktarist

Big Muff, Hot Cake, or any Zvex distortion pedal.

But, if your up for spending a little more money, I'd recommend getting the Lovepedal Kanji Eternity Overdrive to pair up with another distortion pedal (it can even be a cheap one like the Boss DS1). I pair mine up with an MI Audio crunchbox distortion pedal (pretty nice sounding pedal, not the best, but I got it for a good price). COT 50 might actually be your best choice in regards to a boost pedal.

Proguitarshop has some great pedal demonstration videos: proguitarshop.com

peace,
-nick

asshat

does the amp have any knobs that specifically say "gain" and "distortion"? If it does it's probably from when they started putting those presets on amps.

I've got an old fender vibrolux that I play my muff pedal and fuzzface through and it sounds pretty awesome. If you wanna play anything post-maiden though it's probably not the right amp for you. I'm sure theres enough pedals out there to make it more to your liking.

I'm thinking of those boss pedals with like a million different presets that cost about $400. I don't know what they're called.Any kind of pedal that says "metal" on it.
....electro-harmonix pedals tend to sound more old-school. any of that line 6 garbage would work too.