Basically i have just checked on the list of compatibility, and this board does not support any quad core cpus (775 socket). It supports only cpus LGA771 Socket.
Here are the list of compatible cpus:
There are two types of this board:
(i) Non- Refresh Board (old)
(ii) Refresh Board (there is a letter 'R' at the end of the sku)
Apparently, your one seems to be a non-refresh board as there is no letter 'R' at the end of the sku code. If your board is non-refresh version, it is compatible with only 65nm cpus from the list not 45nm cpus. So please make sure you double check before getting a cpu.
How to check if your motherboard is compatible with the 45nm cpu?
If your board pba number is on the list, it will work with the 45nm cpu.
Please note before changing your cpu, make sure to update the bios, bmc and sdr firmware as a precaution. As some cpus need a bios update in order to work with a certain board revision.
Here are the list of compatible and tested memory:
Hope this will help you to find a cpu and memory. If you need more help, reply with your board pba number.
I think 5300 processors are supported. Basically 65 nm processors should work, they only say it is incompatible with 45 nm processors. Also on the top of the page you are refering to they say "not all boards are compatible with 5400 and 5200 processors" - both those series are 45 nm, Quad Core and Dual Core. But 5300 series is Quad Core on 65 nm and it should work.