When I was thinking about doing similar mods a while ago (before my wife decided the money was going on housey type stuff
) I spoke to REVO, JKM and Superchips.
Superchips said that it was fine for their version of stage 2 to just have the downpipe as it was that and the cat that made the biggest differences.
REVO and JKM both suggested that it wasn't actually all that necessary to go to stage 2 with those mods as they could tweak the stage 1 software settings to compensate for the improvements. They said with the full TBE it would make the most of the stage 2 software but with just the downpipe and cat it was still often within the parameters of stage 1.
So basically what we have here is tuners grade their software to their own specifications. As you already have Bluefin I'm sure they could sort you out with what they deem best and that would help keep costs down.