I've got over 25 yrs worth of exp. @ troubleshooting pc's & I agree it either has 2 be a settings or driver issue, or one with your videocard. I assume that by GF7600GT you mean GeForce or Nvidia, same kind I use religously, you may want to make sure you have your drivers updated & go into the Nvidia control panel under Performance & Quality Settings; If you have a checkbox for Show Advanced Settings, check it,
Set AntiAliasing Settings, Anisotropic Filtering, & Vertical Sync to Application-Controlled. {Unless u have a OLD CRT Monitor then U need 2 change ONLY Vertical Sync to ON.}
Set your Image Settings to High Performance, Force Mipmaps to Triliniar, (Make sure Conformant Texture Clamp & Extention Limit is OFF!) Set Hardware Acceleration to Single-Display mode {Unless U use multiple monitors}
Set Trilinier Optimization, Anisotropic mip filter Optimization, Anisotropic & sample Optimization to ON.
If you have a separate Tab for Additional or Advanced Direct3D Settings, Look for this box: Max Frames to Render Ahead- I'd set it to @ least 12-32.
Your system hardware seems more than capable of running Spring without any lag. How much Ram do you have & what OS & What is your Internet Provider?
The system I use most often for playing spring is Running XP-Pro on an old PN-8 Mbo VIA Chipset which has a 1.5Ghz Pentium-4 {Williamette} on a Socket 478, 400Mhz Bus, 512 Megs of PC-2100 (266Mhz) DDR
with a Western Digital hard drive {ATA-100 IDE-NOT SATA} & my Video Card is a original Nvidia GeForce 5200 {128Meg version} NOT the new one with the Dual 400Mhz Ramdac's.
The video card's Clock is about 250Mhz & the on-card ram is about 333Mhz. I can use this PC to HOST games between 4-6 Players & rarely have any problem.
Also Check to see what other Processes may be eating cycles in the background, & many forms of Spy/Malware are notorius for this.
My advice is play in Single Player before changing your settings around & to see if you encounter the same problems. Then Adust things gradually, You should be able to notice a change right away. If you don't it could be your 'Net. H

pe this Helps!