Yes... one of my friends had also ordered this sapphire 7950 OC from flipkart and they cancelled the order. Apparently it seems either they ran out of stock really or had got the pricing horribly wrong as no other shop was offering that card for 25k and no other 7950 OC cards were available.
That card will fit your 400R and GS600 is more than enough. I could fit that card in CM Elite 311 too and could run it of Antec VP450 as well
Asus HT7950 DCII which I bought is priced at 29K on flipkart. 3k increase in pricing considering I bought it for 26k just a month back. This all is happening since Flipkart are confused about pricing of AMD cards right now.
Get HD7870 cards like this one for 25k.
HIS AMD H787Q2G2M 2 GB GDDR5 Graphic Card | Graphics Card | Flipkart.com
or if the price fluctuations don't worry you much then go for the Asus one which I bought priced at 29.3k on flipkart.
Asus AMD HD7950-DC2 3 GB GDDR5 Graphics Card | Graphics Card | Flipkart.com
But one caution, on Maximus V Gene, you'll need to buy a two slot card in future (hence another Asus DCII card will be out of question), if you need to crossfire. Put it in first PCIe slot and put the Asus one in the bottom slot as Asus HD7950 DCII is a triple slot beast.
Sapphire HD7870 OC Edition is a gr8 option too... but I really doubt Sapphire's availability with Flipkart.
*www.flipkart.com/sapphire-amd-ati-...B4ZR&ref=81551c9e-008b-4bb5-a0ca-828573035880