yes, i think an overdrive pedal is just what Sam wants. just to add that fuzzy edge to the distortion, although it can end up being very noisy. if you can use the effects only from the POD, try the tubescreamer model, it's not a big distortion pedal on it's own, but to tip an already driven amp into meltdown it's perfect! although i also use a marshall guv'nor for a more aggressive (and noisier!) brand of mayhem.
also, try using the POD as a volume boost by setting it's output level higher, just to see will a boost pedal have the kind of effect you're after. the POD might not give you exactly the sounds you want, but it will give you a good idea of what the real thing will sound like and show you what type of pedal to go for.
