AJP you're so flipping right there with the 4wd an all that as power down on a gti ed30 fwd car. Maybe I'm being silly but I was thinking R32 ?
All depends on your long term plans for the new car power-wise, but also what else the new car gives you that the GTI doesn't (apart from power).
If you're not planning on 300+ bhp, then sticking with the GTI is the better option. A Stage 2+ GTI at 285bhp will arguably be nicer to drive than an ed30 at 285bhp as the smaller k03 spins up a bit quicker than a k04; it'll certainly feel more lively.
As for the R32, matching a Stage 2+ k03 GTI in the power stakes will be tough, definitely expensive, and maybe even impossible, unless you fit a turbo/supercharger kit. That said, I'd imagine you could get close to peak power of 270bhp on an R32 with exhaust manifolds, full exhaust, intake, map etc. But, and it's a big but, it'd be a real lesson in 'peak power isn't everything'... If you put a 270bhp k03 GTI on the rollers, and a 270bhp n/a R32 on the rollers, the area under the GTI curve would be much, much larger. In short, a GTI at 270 would be so much more gutsy than an R32 at 270. And you'd feel it.
So then you've got to ask yourself what the R32 can give you that a GTI or ed30 can't. The noise - glorious. Bucket seats. That gorgeous metallic blue.
I'm personally not that keen on the R32 front end, nor am I envious of the tax and fuel costs. But that's your shout!
So... back to the original idea. If you're buying an ed30 to go Stage 2/2+, then go for it. You'd be 80/90bhp up on the equivalent 2+ k03 GTI. But if that's not the main reason for doing it, and you're not planning on 300+ bhp, stick with the GTI (or get the 32 if you fancy the bills and soundtrack).
Your GTI can do 285bhp. In its stride, reliably, and arguably better than an ed30 at 285bhp.
You don't actually get a full-fat k04 setup with an ed30. The brakes are 312mm, like the GTI, with the same calipers. The intercooler is the same. Something with the proper CDL engine would be a much better bet if you're changing cars to chase big numbers.