We've got a VL turbo, doesn't have the rb25 head though, just all RB30, and it's got a haltech E6K..
But as Dave said, theres no point coming this far and then skimping on the most important part. I'm not sure of the specifics between haltech and microtech, but our haltech works well.
Our VL's mostly (I say mostly.. because I think redcliffe dyno did the original tune) been tuned by Matty Spry, although he hates the car (long running joke), I'd have to say he's the best all round tuner in SEQ. ... maybe even QLD or Australia!! (big call!)
He's also tuned our skyrice numerous times and I wouldn't go to anyone else now.
He's straight down the line with no bullshit.