I've been spending my usual FFR forum reading time these past few days on EZ30R swaps. Engines can be had for about $1500, but expect to spend about the same or more on engine management. So it'll cost you about the same as a version 7 or 8 EJ20. And on top of that you'll probably need different headers. Once the STI transmission is an option, the EJ can "fairly" easily be bumped up to 350+hp. Much more and you'll need to look at internals. Not sure how many EZ30R's are turbo without building the block, but once you do the sky is the limit. If 300-350 is your end goal, H4 is your best option. But if you feel the need to make 500hp+ on pump gas with a usable powerband, well, bring your wallet and build that EZ.

Again, no expert here, just info I've gathered online in a few days.