Don't do it. The performance benefit will be negligible at best, for quite a high risk of frying the hardware, since it's a hardware mod.
Second, Dreamcast was never supported, except that it ran early, and very slow, 1.08 builds when the porting work was actually being done. The DC could never run 2.0.4 because of hardware limitations.
You're better off helping us port to Android so we can get it on Ouya in the future. SRB2SDL needs to be ported to SDL 2.0 once that is stable (w/ full Android support) before that can happen, unless you want to roll with your own OpenGL context and sound code.