I only have experience with the OS RG and the JP-1 pipe. I'm quite happy with the value/performance ratio. As you say:
The OS RG is certainly reliable and certainly cheap (price wise). Is it powerful enough for what you want?? Depends. Its not a screamer like a V-spec, but has nice low end grunt. You didn't indicate what engine you are replacing, or which buggy you're putting them in, so I can't say if this combo will be better than what you had. For those on a budget, I feel you can't go wrong. My $.02