Please advise on upgrading my system

I have Win2K (SP4) and I can install Windows XP Pro SP2 if I want.

I have FS2004, Active Camera, Active Sky, FSNavigator.

My machine is as follows;

Dual Xeon P4 2.2ghz
1gb rambus Ram,
Supermicro P4DCE+ Mb,
PNY Quadro 750gxl 128mb graphics card,
10K2 Atlas 18gb scsi
200gb Maxtor diamondplus 9
250gb maxtor diamonplus 10.
21" monitor.

I'm not happy with the settings I'm getting on this system at all,
"moderatly low" is giving me around 20fps and some jitters (sometimes
much lower fps).

The machine is a very lightly used machine, not much software on it.

My belief, and excuse me if I'm wrong, is that I could upgrade the
graphics card and this would improve things somewhat. My motherboard
supports AGP 4x Pro and on Ebay I've seen a Radion X1600 PRO 512MB DDR
card for sale at £95.

Firstly, I'm very ignorant in the field of graphics cards, will this
card that I've seen on Ebay work well with my system ?? It says that
it's agp 4x/8x compatible but will my mobo get the best out of this
card or will it be too good for my mobo ??

Please advise as I'd like to see fs2004 in a much better light than I'm
currently experiencing.

(I have applied some tweaks to the cfg file and used the utlility to
stop services that aren't necessary)