Which to upgrade Dell Dimension 8300 or Dell Dimension E310

Hello again to all.  I wanted to thank again many of you whom have helped me in the past with all of my questions.  I am trying to decide on which of my ancient computers to try and upgrade so I have at least one "fairly decent"  older machine that can attempt to run some older programs, and maybe even some newer games on lowest settings.  I basically got both of these machines for hardly anything, and would like to see what I can get out of them.  The 8300 is unfortunately a 2.66 Ghz and accodring to some here the  cpu is only upgradable to a max of 2.8 due to the ago of the motherboard.  I have a 512mb/256 bit X1950 pro 8X agp card and 4 gb's of ram.  The E310 is a 2.8 Ghz HT and I have a 512mb Zotac gt 430 std pci video card with 2 gb's of ram.  As I know many of you are thinking why bother they are both ver outdated..., but I have them, they were near free, and I like working on all technology so there you have it.  I can get a 3.4 ghz sockt 478 cpu for under 20.00 for the 8300, but good chance it will clock down to a max of 2.8 gz due to age.  The E310 I can get a 3.8 ghz cpu for around 17.00, but do not know if this will have the desired effect I am looking for...better results with performance with some games, etc.   Any help, advice would be greatly appreciated.  Again, I know that these machines are older, and have many limitations so if that is your only response please keep in mind I am already fully aware of it.  Thanks