I couple my Ibanez tube screamer TS7 to my DS1. That way I get two different types of overdrive from each of them, and a cool lead tone from both switched on. All this without tweaking the controls. The TS7 has this hot button too which can also give you the screaming tone coupled with the DS1. I do not feel the need for a metal effect.
I finished making my tube amp, so I might sell my TS7 if I get Rs. 2500.
Ibanez GSR390 Bass guitar (might sell if i get a price)
Laney RB30 Bass amp (might sell if i get a price)
Bunch of Boss pedals