Quick memory question!

[Kerplunk]

I have a AMD64 3200+, 1GB RAM, Geforce 7700GT 256MB

Would I notice much, or is it worth installing another 1GB ram?

I have an MSI K8N Neo2 Plat. mobo which supports DDR memory, would the below be ok?

http://www.overclockers.co.uk/productlist.php?groupid=701&catid=8&subid=145

I currently have a 1GB Geil stick, can I mix and match vendors?

 

[Cob]

Yeah you'll notice the difference with another 1gb.

It's hard to tell if they'll be compatible without trying them tbh.