I'm having some problems and I'm apparently needing to buy a new DSLR body. I'm leaning toward the 60D but haven't ruled out the possibility of the T4i or even just replacing my T1i. Because of this, I'm wanting to consolidate, sell some old lenses and maybe buy one new lens, if possible.
I have the Tamron 18-270VC and I think I'm going to keep it because I can leave it on the camera all the time and I'm good to go if almost anything pops up. I have the EF-S 55-250 and I think I'm going to sell it even though I think it might take slightly better quality photos than the Tamron, it's just a flexibility issue and I think I'd like to choose one and dump the other. I also have my kit lens from my T1i that I like well enough and will keep. In addition, I have some assorted short lenses and an older Tamron 18-200 without VC that I think I'll sell.
I think I'm considering purchasing the Canon EF 70-300 f4/5.6 IS/USM but I don't know if it's that much better than the 55-250 or the Tamron 18-270. I also have the Kenko Pro300 DGX 1.4X extender, for what it's worth. Although I know that I don't have the "right" combination of lenses, I'm trying to get buy for general and wildlife photography with what I can afford. Please don't tell me to save my pennies for now and get a good lens, the new body is mostly breaking the bank and the sale of some of my older "lesser quality" lenses will be used for one moderately priced lens (probably either that 70-300 or the 100 non-L macro).
Thanks in advance, mostly curious about the EF 70-300.

