You are saying what you want, some sort of prime lens and a larger zoom, but you are not telling us what purposes you need them for, which makes a thought out recommendation impossible.
Also, if you get one of the cheaper fixed primes in the focal range of your 24-105, you're just going to get a lens that can operate at lower f-stops, but not at top it's optical performance, in particular while in low light when it's most needed. That is not to say it isn't usable or perhaps even very good, but it doesn't seem to give you a ton of extra usage that you don't already have in that very nice 24-105 lens so I would want to know specifically what I wanted it for, and not just to say I owned a prime lens...
As far as telephoto, see if you can't try them out first, since the good ones are indeed very expensive. If the 70-200 is long enough for you, then you have your lens, as the IS II version is the best of the best in telephoto zoom. If the length on the 200 end isn't quite enough, or if it's too big and heavy for most of your uses (which is my problem), then you are going to have to make a very personal decision, and I would recommend reading up on and testing all of the options available, including the option of 70-200 with tele-converter(s), 100-400 IS, 28-300 IS, and the rumored/upcoming/possibly costs a fortune 200-400 IS with built in extender, as well as the 70-300 f/4.5-5.6 DO and the newer f/4-5.6 options, as well the older 70-200 lenses, like the f/4 option, are both lighter and cheaper, so this is a consideration as well and is likely why they still exist on the Canon line-up. The list doesn't stop there either when you consider non-Canon options, discontinued value options, or EF-S mount options that DON'T work on your fullframe but can still deliver in a smaller size if you pick up a second, relatively inexpensive body for a smaller total size and weight option.
Also, spend some time sifting through this site http://photography-on-the.net/forum/showthread.php?t=141406
I have looked through a variety of lenses on that site, all used on different bodies, and I've said this before, but what became quite apparent is that the equipment they make today is just awesome across the board. The bad pictures you find, you find them even on the very best lenses. And it's because good lenses and nice camera bodies on their own (going by today's equipment) don't take amazing photographs. And even when I see bad pictures, poorly composed, poorly lit, improper settings chosen, /not good art photo's, I can still see what the lens was capable of and can't fault the equipment. What this means to me is, you pick out the lens by it's size, weight, focal range, f/numbers, price, features etc., based on what your needs are and how useful that lens design would be for your needs. If you don't do this, you will still have great equipment but you won't be well thought out, and you might not even be able to answer these questions right now. I heard a great piece of advice on here a few weeks back. Don't buy too many lenses at once. Take the awesome 24-105 you have now (that's an amazing lens with a really useful range) and just go shoot as much as possible, forget about what you don't have, and find your style, what you like to do, and also what you learn that you are having trouble doing/can't do with your current setup, but really want to be able to do in the future. Then you will know what you need most. Or you can just buy 1 of everything Canon makes, and you probably will never even be able to leave the house as you won't have a clue as to what to bring with you...
