I was offered just over £4K against a 05 STi with 7000 miles about 6 months ago but bought an 03 with loads of extras from subaru and got £6k as a trade in but the price to change was nearly the same so it's all about personal choice, a newer car that costs less but will be worth less or an older uk car that'll probably be worth bugger all in a year anyway !
Personally i like the shape of the STi 8/9 and would try and get a deal on one seing as there old stock now.
Stan palmers in carlisle had an STi 9 on a 06 plate for £20k a wee while ago.