Dell Dimension 4700 Graphics Card Upgrade?

The processor on this machine is at 4.8 on the WEI scale so going higher with a graphics card probably won't help much.  The new card in the machine is probably overkill for the processing power of the machine, but it was well worth it.  Now I need to bump up the processor in this machine but don't know if it's possible or even cost effective...any thoughts?

Probably either the E8400 or E8500 would be your only worthwhile upgrades as shown HERE, but may not be cost effective. These are the two highest-end Core 2 Duos you can get (except for the pricey E8600) since your Inspiron 530 does not support the Quads.  I can tell you if you had a 530 that supported Quads with a Q6600 that they came with, your WEI processor score would be 7.1.  

If you are happy with the improvement as you mentioned, then it may be best to just stay where your are versus putting any more money into more upgrades since even the Inspiron 530 is an outdated system by today's standards.  As you can see though, getting a better video card makes a big difference.  

Here's a list since I don't know what you have now:

Intel Celeron processor 430                                        
Intel Celeron Processor 420 (1.6 GHz, 800 FSB)
Intel Pentium Dual-Core 2140 (1.6 GHz, 800 MHz FSB)
Intel Pentium Dual-Core 2160 (1.8 GHz, 800 MHz FSB)
Intel Pentium Dual-Core E5200(2.5 GHz, 800 MHz FSB)
Intel Core 2 Duo E4300 (1.8 GHz, 800 MHz FSB)
Intel Core 2 Duo E4400 (2.0 GHz, 800 MHz FSB)
Intel Core 2 Duo E6320 (1.86 GHz, 1066 MHz FSB)
Intel Core 2 Duo E6420 (2.13 GHz, 1066 MHz FSB)
Intel Core 2 Duo E6550 (2.33 GHz, 1333 MHz FSB)
Intel Core 2 Duo E6750 (2.66 GHz, 1333 MHz FSB)
Intel Core 2 Duo E7300 (2.66 GHz, 1066 MHz FSB) 
Intel Core 2 Duo E7400 (2.80 GHz, 1066 MHz FSB)
Wolfdale Core 2 Duo, E8400, 3.0GHz, 6MB, 1333FSB, 65W, E0 
Wolfdale Core 2 Duo, E8500, 3.16GHz, 6MB, 1333FSB, 65W, C0
Wolfdale Core 2 Duo  E8500 (3.16 GHz, 1333 MHz FSB)
Wolfdale Dual Core Kit, E8600, 3.33GHz, 6MB, 1333FSB, 65W, E0