Remaking the line-up

[uplander]

I have just upgraded my camera from a canon 10D to a 40D. I am dumping several of my lenses and will be replacing them with better glass.
I'm booting a Tamron AF 18-200 f/3.5-6.3 and a Canon 70-300 f/4.- 5.6 IS USM and Keeping my canon 100-400f/4.5-5.6L IS USM.
I am getting a Canon 70- 200 f/2.8 L IS USM.
I am undecided as to what I should get to replace the Tamron.
I want something fast and something wide.
I was looking at the EF-S 17 -55 f/2.8 IS USM but I really don't want to buy a lens that is specific for APS-C sensor as I will probably upgrade to a FF sensor camera at some time.
Should I be looking at two primes like a 24 and a 50 or would the EF 24-70 f/2.8L USM be a better choice.
I am open to suggestions also

 

[Big Mike]

The 17-55 F2.8 IS, is said to be a fantastic lens, and probably the best option for a normal range on a crop camera. If you do want to stick with full frame lenses, then I'd suggest the 17-40mm F4 L or the 16-35mm F2.8 L.

The 24mm F1.4 L is a fantastic lens, the 50mm F1.4 (or 50mm F1.2 L) are great lenses as well. The 24-70 F2.8 L, has been a work horse lens for many pros and is well regarded...but I've been hearing bad things about it's focus accuracy from a few pros.

Either way, I feel that 24+mm is great for full frame but is awkward for a crop body. 17mm is great on a crop body and is ultra wide on a full frame.

 

[JIP]

I am a big fan of the sharpness of primes (my 85 1.8 is the sharpest lens I have) and the price for the 2 will probably be better but I think it all depends on what you intend to do with it. If you have lots of time to change lenses or have multiple bodies great go with the primes but if your shooting will leave you needing to change focal lengths quickly I would go with the 17-55. I do think it is good to have at least 1 prime in your bag but I would probably prefer the 17-55.

On a side note:

Good for you for kicking the 18-200 to the curb. Leaving a lens like that behind is a great way to evolve in photography.