Its not that expensive a job if you do the work yourself. Pick up an aristo or supra turbo engine (they are both 2JZ-GTE engines) with turbos, downpipes and all ancilliaries for in the region of £1500 (get them in a crate from Japan for about £900 if you can be bothered with the hassle), a 2JZ-GTE engine management ecu, the loom to go in between and you are away. It will plonk straight in as the 2JZ-GE lumps bottom end and mounts are identical. Thing is I'd look at changing the transmission as well and upgrading to the better TT's box (about £500) drive train including the LSD (trust me you'll need an LSD with that power). You'll also need an intercooler and pipework not sure of the availability or configuration of aristo intercoolers but the one on the supra is a side mount.
Or as the guys say sell the 300 and buy an aristo. Unlike supes there seems to be a lot of aristo's left in Japan still.