Well I suggest better wait and take off a day or two before actually ordering. You seem to be in quite a hurry to buy your new gaming PC, but if you get the wrong components in your PC you would have to suffer the next couple of years.
The quotation offered to you for the hardware components are on the higher side. Although you dun expect to have nearly the same prices in Guwahati as in other metros but do check other shops or distributors nearby or a bigger city if its nearby.
To get an estimate of the prices of components you can check
www.deltapage.com and
http://www.computerwarehousepricelist.com/ pricelists.
Well if you are not interested in having two graphics cards in SLI, then why go for the a8n-sli dlx. Also instead of a 3500+ processor you can very well go in for 3200+ Venice core and save the money for a better graphic card. With the 3200+ you can go for the Asus A8n-e board which would cost round abt 7k. So you now have a better budget for the graphics card if you are a gamer and wont be upgrading any time soon.
Cross check the other component prices and ask your dealer to give you a better quotation.