iMac goes into repeated reboot cycle after upgrading to El Capitan

Hi,

I use an iMac (20", Mid 2007). I have upgraded the memory to 6GB and replaced the hard disk by a 256GB SSD.

I upgraded to El Capitan and the system goes into repeated reboots. Post power on, Apple Logo comes up and then the system restarts again.

I have tried the following:

1. SMC reset

2. PRAM reset

3. Booting in Safe Mode

4. Format SSD and reinstall El Capitan

None of these have worked. I had faced the same problem when I tried using the El Capitan Beta as well.

I have now moved back to Yosemite. Restored from my Time Machine backup. Works well.

Should I leave my El Capitan ambitions behind? Could someone help please?

Thanks in advance,

Regards

Murli