Just to make sure you realize what you are getting into.  In about 19 weeks the block reward will drop to 25 BTC per day.  While that has been known for a while, nobody knows what the difficulty will be by then or in the months after.  What is known is that difficulty has been steadily rising again, even with this deadline looming as the rising exchange rate has caused profitability to rise to relatively high levels.

Anyone with near average or above average electric rates will likely not be able to mine profitably come December, unless the exchange rate rises above $10 or so.    So unless you pay under $0.10 per kWh, you might want to rethink buying a new GPU card if the only reason you are looking to do so is for mining.

The other wildcard is the date for when ASIC designs ship and in what quantity.  They have the ability to completely obliterate GPU mining profitability in just a matter of days.

Now if you were considering a GPU card for gaming and would mine on it as well, then none of this really matters, you mgiht as well go for it and get a few months of decent mining revenue while it lasts.