when i bought my ti i had Dx9 cards in my mind but my budget was low then, so i opted for a ti4200 which was far more powerful then 5200 and cheaper than 5700(which also lacks behind in performance when compared to ti) .I had played halo which is a Dx9 game on both the cards and i had to turn off the "eye candy" options and lower the resolution to play it decently on a FX5200(one of my friend has it) , on the other hand i played halo on my Ti4200 on full settings with all the eye candy turned on with the resolution 1024x768.It's really hard to figure out the visual difference in DX8 and Dx9 cards when u play games like halo but the Major issue is of performance the card is providing u.
I repeat if u really want to experience the perks of Dx9 technology then 5200 is not a good choice, u will need at least a 5700(still weaker than my ti4200 128MB 275/550) and 5700 is more expensive than a ti4200. and if u want proof just hav a look at the link that alphaomega suggested and see the excel file abt comparison of 80 gpu's.
and i wud like to highlight this again which is from that excel file on
www.3dnews.ru
3dMark 2001 se
FX 5200 ------------------- 5992 3d marks
Ti 4200 ------------------- 11640 3d marks
Ti 4400 ------------------- 12510 3d marks
3d Mark 2003
FX 5200 ------------------- 692 3d marks
Ti 4200 ------------------- 1733 3d marks
Ti 4400 ------------------- 1798 3d marks
Splinter Cell (1024)
--------------------
ti4200 = 27.9
5700 = 18.7
UT 2003
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ti4200 = 82.2
5700 = 72.2