urruko... you can have any custom firmware you like...the reason you couldnt get to custom firmware before was because there was no downgrader for your firmware, however yesterday the downgrader was released you can find it here
http://www.noobz.eu/joomla/news/downgra ... mware.html
I believe kingcoke also posted the tutorial for it in the tutorial section (its pretty much a copy and paste of the readme that comes with the downgrader) You'll need a copy of lumines as well to be able to downgrade which you can purchase from that link as well, or just rent a copy from your local video store.
Anyways this downgrader will bring your system firmware to 1.50. Once your there you can upgrade to a custom firmware of your choice...i prefer 3.03 oe-c but others prefer 3.40 oe-a its all up to you. 3.03 oe-c winstaller can be found here
http://forums.afterdawn.com/thread_view.cfm/460892 and i believe theres an easy installer for 3.40 oe-a on this site somewhere.