Its not the fact that its an older board. I did the EXACT same upgrade. The M3A32 MVP Deluxe DOES support the Phenom II. You do need the latest BIOS but not having the correct Bios shouldnt cause the symptoms you are seeing now, not having the right Bios the computer should still boot but the CPU will not properly be recognized.
You said you tried flashing the BIOS. Did you manage to get anything on screen to actually try the flash or did you simply mean you put the files on a USB stick and tried to boot still with no success?
When you reset the CMOS, was this with the old processor in. If not reset the CMOS once again with the old 6000+ in the board.
This is a long shot but I've done it to myself. What type of monitor are you using? Do you have more then one input on the monitor. I have an LG monitor with two inputs and a button to switch between them. A few weeks ago I was finishing up a build I was doing for a friend (coincidentally it was my old M3A32 since I upgraded to the M4A79). I switched out processor fans and when I cut the computer back on I couldnt get anything to display on the monitor. After reseating the processor, then video card I finally realized the problem was that the monitor I was using automatically switched to the other input when it didnt detect a signal on the input i was using for this computer. All it took was me hitting the input source button on my monitor.