Panasonic Lumix G1 or Olympus E-420 or Olympus pen E-P1

Hello there! This thread is also at the micro fourthirds forum. I was a owner of a Olympus E-300 since 2005, but recently the shutter stopped working and so I'm stuck with a dead weight and the 14-45 and 40-150 lens.

I can buy the lumix G1 for 200 euros, but it comes with no lens. Although I think it's a great price, I'm reluctant to buy it, because I'm afraid the price of a m4/3 lens is beyond my budget; I don't know also if the af would be sactisfactory with an 4/3 lens adaptor.

The Olympus E-420 can be had for 150, no lens. That would be no problem, because I already have the two lenses I've mentioned; by the other hand, the lack of stabilization is something I can't shake of my head.

Finally, I can buy the pen E-P1 for 170 euros. Have you found the lack of flash and optical/EVF finder to be problematic?

Which one is the best choice, in your opinion? Where would I gain a substantial gain in image quality?

Sorry for my english, and thanks for your attention!