Ankit,
Besides price, you are right in considering weight as well. If a lens is too big and heavy for you, then you're not as likely to use it. If you have a pretty large budget, then the 50-135/200 combination would be ideal. If your budget isn't that big, then perhaps a 50-135/TC combo would work.
Have you considered the Sigma 50-150/2.8 EX HSM II? B&H has it for $749.00, so it's in the same general price range as the *50-135, but it gives you a little more range on the tele end.
Overall, though, I think the best bang for your buck is the 55-300. It's definitely a step up from the Tamron/Sigma 70-300s and it's about half the price (or even less) than the *50-135 or 50-150. Mine will be delivered on Tuesday, so I'm anxiously awaiting it's arrival. Once it's in my hands, my Sigma 17-70 won't be lonely anymore.
Even if the *60-250 was affordable to me, I still might not get it because of the weight alone.
Heather