Be careful of the EJ20Rs. Seems a lot of people have had head gasket issues with theirs of late, and Al posted something on RSLC about them not getting forged pistons. Thought about going new EJ207 + 98 WRX heads? You've got all the other shit you need to get it running and at least you know it'll last without chucking a tanty.
Flip the intercooler, too. Short piping FTMFW. You could even sell the TD05 for $250-$300 and buy a VF23 for not much more, and the 23 is a much better turbo (which can have its housing rotated for uber short pipework awesomenessoscity). I liked TD05s but after going VF its such a better turbo. And you can get them built up to be a PE1820 clone if you want to go silly (like the one I've got FS :P

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I reckon with your WA summers I'd chuck parallel fuel rails on it, too. Might as well do this shit while you're fucking around in the engine bay to save hassle later on. Add V3 STi 440s and an adjustable fuel reg and you're on a winnar. Add a V2 STi RA ECU for more awesomes - my car fucking CRACKED with that ECU. The tune is far superior to Aus-delivered ECUs, but you do need to make sure they've got adequate fuel.
For coilovers are you thinking of going Teins? I ask because I reckon they're not worth the extra money over a set of STi pink springs on STi struts. I've compared 2 Libertys back to back with those suspension set-ups and the spring/strut combo rode better, cornered just as well and was much quieter and cheaper. If you want maximum awesomeness, a set of Whiteline Group 4, Buddy Club Racing Spec Dampers or Bilstein PSS9s are the entry level, with Pro Flex, properly valved DMS coilovers or some Apexi Pro units would be even more awesome.
I'd also have a good look at your trailing arm bushes after putting in stiffer suspension. The Libertys seem to wear them really badly with hard cornering.
PS: needs 6-speed!