dont go for a blitz or mines etc etc, there not reprogrammable.
unichip is a good alternative, i'm not sure on the specs but i beleive its very similar to the emanage, this unit also has to be tuned by special dastek approved installers/tuners, i was quoted £630 all in for this fitting and mapping.
then you have the emanage blue, excellent specs, proven time and again, and a site favourite. unit from a trader is £355 + fitting and mapping it will cost around the £600 mark in all.
there is the ultimate emanage but thats an extra £100
also the apexi safc/neo, but this is no where near as goood as the unichip or emanage. this is just a cheap quick fix.