There is also a version P3.4 for the K/40 now, as well as a P1.4 for K/00. Go to
enter DVDRW824K as model number, and find them all. Warning: Philips has changed their flashing tools, and firmwares are now 'embedded' in the .exe as opposed to in a separate .cvt file. A wild guess, this is probably to tackle on the practice of flashing K/00 (+R only) units to K/40 (+/-) firmware to bypass their official pay upgrade to P2.2 (+/-).
Apparently the P3.4 firmware doesn't officially support K/20, unlike P3.3 which did, and there's no new firmware for K/20 yet. Many K/20 users successfully upgraded to P3.3 in the past, others had problems, IIRC. If you upgraded K/20 to P3.3 with no bad consequences, P3.4 might work for you. If you're still at P2.x and have no problem like media incompatibilities, you might want to stick with it instead of trying a P2.x -> P3.3 -> P3.4 upgrade.
Also I'm not sure if upgrading a K/00 to P1.4 could prevent you from flashing it to P3.3 later. Again flashing a K/00 to P3.3 worked for some, but is something you do at your own risk.