Motherboard frying PSU - Maybe time to upgrade?

Hi all,
I have a slightly outdated system, altho I still haven’t managed to make much use of it over the last few years due to work.

Asus P5Q Pro motherboard, Intel Q9605, 8GB DDR2.

A while ago, it just stopped firing up, so I just guessed it must be the board and bought a replacement on ebay. Then subsequently found that the power supply was dead, so replaced aswell that and I was back up & running. I had already he swapped out the motherboard, so I left the new one in and just kept the original one as a spare, believing I was just made a mistake thinking the board was dead, when in fact, it was the power supply.

Recently, my PC stopped keeping the clock time and also wouldn’t remember which disk to boot from, I had to keep giong into BIOS to select it and reboot, then set the time & date in windows. This made some of my plugins fail. I got Windows XP/32 on 1 drive and Windows 7/64 on another, I don’t know if this causes any problems?
I found I couldn’t set the time/date in BIOS, it just wouldn’t allow me to change it, so I updated the BIOS and still no change, so I thought maybe the battery or a board issue, so I just put the old board back in, believing it was still ok.

Now I got another dead power supply, so I guess that motherboard must be killing the power supply.

I ordered a new power supply, a replacement battery for the board and will try 1 last time. This system is still plenty powerful enough for what I want to do, but if I can’t get it to run right, then what’s the next newest thing after the P5Q? I don’t want to trust buying another one if indeed 2 of them have now failed.
I also don’t wanna spend a fortune on the latest board & chip, so I’m thinking maybe an early i7 with DDR3, but which board? Need 2x PCI & 2x PCIe 4x SATA.