g110yd, Sorry, but neither of the models you listed support 10GbE upgrades.  You can get additional information about what models support controller upgrades in the Configuration Guide en.community.dell.com/.../2639.equallogic-configuration-guide.aspx -joe
We have an end-of-life PS3900XV that is still going strong.  It has two Type 3 SAS controllers in it.  Can you upgrade controllers?  If so, how new can I go?  Type 4 SAS?  Type 7 SAS?  Newer?
Can you put newer controllers in older systems?