Darn, wish I could work out how to edit a post, it'd save me from creating a stream of newbie waffle on here.
Note - the TD04 spoolup time (i.e. lag) and performance will be very dependent on what sort of TD04 you use - they're not all the same. Exhaust housing and turbine wheel / compressor wheel will all have a bearing on max boost and spoolup, as will choosing a hybrid (ball bearing) CHRA in place of the standard sleeved bearing.
Also you have to bear in mind the stock engine internals will only be able to stand a finite amount of boost, so if you choose a turbo which e.g. could go all the way up to 300bhp, you may well find you actually get 0 bhp since the massively increased boost will wreck a standard engine.
And finally you have to look at the insurance implications, whilst a standard gt1446 might only result in a small premium increase since it's a factory fitted turbo, fitting an aftermarket one might make your insurers see £££ signs...