[FLAiTE]

Hy.
I have a Counter-Strike 1.6 Server that runs on a Windows 7 Ultimate x64 machine, with the following hardware specs:
CPU: AMD Athlon II x4 640 @ 3GHz + 3rd party cooler
RAM: 4GB DDR2 @ 800MHz
GPU: Radeon HD4890 New Edition 1GB GDDR5, 850MHz GPU clock
HDD: WD 300GB S-ATA1
MBD: GIGABYTE GA-MA785GM-US2H, R1.0
PSU: Enermax NAXN 450W

Internet connection: 100Mb/sec fiber-link
Server slots: 26

My server really doesn't run very well. It's laggy when you fire the weapons (not in regarding the ping, but in what regards the smooth play).
I'm not using any high traffic plugins.

I installed MMTIMER and set it on insane mode, with a sys_ticrate of 10.000 => the server runs flawless. The core1 of my CPU is @ 100%, cores 2-4 are @ 0/5%. Not a big deal, as it operates at 39°C => the FPS are oscilating pretty much between 9999 and 1500.
If i set it with insane mode off and sys_ticrate 1200 the fps are pretty constant around 1024 (+/- 50)

What is the optimum FPS for a HLDS server to have a great smooth play?
Should i use Windows XP? (i had a few years ago a great server that runned on windows xp and it was fantastic)
What is the best FPS booster?
What would you recommend for my server?

I don't have anything else running on that machine - it's all dedicated to HLDS.
Thanks in advance!