No rear caliper will ever work well or properly, so forget that totally. I've had a set, and they were ****, so I sold them on very quickly.
it really depends how far you want to go and how much you want to spend.
No Porsche setup will be cheaper than LCR brembos, I know this for fact, having had several seats of each.
The 'entry level' decent porsche setup would be to use boxster front calipers, on 312mm discs. Carriers are available for these for around £100. These apparently work pretty well, although I'd personally be dubious about their ultimate track capability due to keeping the small 312mm discs which just can't take the heat of stopping a heavy car repeatedly for extended periods. For most people they're probably fine though. these will fit under a standard 17'' wheel no trouble. Westy can advise on cost, but I'd imagine this setup would set you back around £500.
The next step up, and in my opinion the best, is to use 996 911 front calipers from a 996 C2 or C4, but NOT a C4S or Turbo. These calipers also came on the Boxster S and are perfect. These will fit under a standard 17'' s3 wheel with room to spare.
These will run on a 330x28mm disc available in 2 piece form from places like Badger 5, or in single piece form for an Alfa brera, but will require the PCD redrilling to 5x100 to use them. I've had these, and they were amazing. One of the best brake setups I've ever had. Cost wise you're looking at around £800 for a full set with refurbed calipers and new single piece discs redrilled.
Beyond that, you're looking at 996 Turbo front calipers on R32 334mm discs, these are pretty monster and beyond most peoples needs, but incredibly nice if the budget / bling factor dictate it. Typically these will require 18's or larger, and almost certainly spacers too.
the final 'step up' in porsche brakes is Cayenne 6 pots, although these are typically overkill and more show than go in my opinion, although I'm sure they still work pretty well, some people question pedal feel with these.