smeezekitty :
Those are both pretty much terrible cards.
You need to get atleast a GT630/Radeon 6670 to really get decent performance
In terms of gaming, those are the cards which can make a difference, however the price is over the budget for you - NVIDIA CLUB-3D GT 630 2GB
http://www.autechnologies.com/graphic-cards-nvidia-nvidia-club-3d-gt-630-2gb-pakistan-p.2767.aspx and this card will play your games on low settings only, no fun.
6450/610 are cards to watch HD movies, not to play games.
So, if you can not squeeze extra from your pockets - I really can not endorse 6450/610 cards. You decide.
In any case, follow this little guide for your future choice
THIS POST APPLICABLE TO MT (MINI TOWER) FORM FACTOR ONLY.
Unfortunately no card that is more than 7.5 inches long or 2 slots wide will PHYSICALLY FIT inside the case - it was found that only single bracket video card can fit due to BTX MOBO, where card internals facing upward towards PC internals, not ATX, where dual card design is blocking another PCI slot by facing downward.
If you prefer the card with beefier fan, then the length of the card must not exceed 7.5 inches, otherwise only "skinny" single bracket, single slot cards can physically fit.
Pictures below will prove my point.
View shows no room for dual bracket
Single bracket only, or you have to cut dual bracket in half
This is the other way to show my point
Here you can clearly see only single place for the bracket
Visual explanation
7.5 inches explained, also shown "obstacles"
This is the picture of actual "skinny" single slot video card (not sure which model)- perfect, "glove" fit.
Unfortunately there is nothing I can help you with based on your low budget.