I've been a SLR owner for about nearly 4 years now. I own a 60D body, 24-105mm f/4L IS, 100mm f/2.8L IS Macro, and 50mm f/1.4. I also have a 430ex II speedlite. I have about $1600 in cash and I'm not quite sure what to spend it on. I have a 9 year old so she is my main subject. In the past 12 months I have photographed indoor plays, outdoor Easter egg hunts, night time "bonfires", swimming pool shots, football games (she's a cheerleader but I really enjoy photographing the players), and I will be photographing indoor basketball games under crappy gym lighting. I don't shoot a lot of wide angle and a bunch of my shots would be considered sports action or portraiture with pleasing blurry bokehs.
No one probably cares about the process, but I want to illustrate that I have had a ton of different lenses. I started with a Canon XS which was upgraded to a 60D after two years. In regards to lenses, I had the kit lens (18-55mm) which I eventually upgraded to a 24-105mm f/4L USM. I started with a 75-300mm which was upgraded to a 55-250mm after one year to a 70-300mm (briefly) to a 70-200mm f/4L USM (briefly) to a 70-200mm f/2.8L USM (briefly), to finally nothing. Finally, I had a 50mm f/1.8 which I upgraded to the 50mmm f/1.4. And I picked up a 100mm f/2.8L IS macro along the way.
I like my 60D, but I would seriously consider upgrading to a 5D mkii if I find a deal for around $1200 which isn't completely out of the realm of reason if I sell a bundled printer and the kit lens (24-105mm).
I think the biggest thing about upgrading bodies is that I will have Micro auto focus adjustment... and while I was underwhelmed by both 70-200's I had, I think if I am able to 100% lock into my target, I would be substantially more pleased with the results. But I'm not sure I'm willing to go back to that well of disappointment. Maybe I might dip into 70-200mm f/4L IS or the 70-200mm f/2.8L IS mkii (the non IS f/2.8 was heavy, but it really didn't bother me so I doubt the IS version would cause me to complain). But IS shouldn't be a factor since the shots I were taking were at 1/4000 of a second or faster... so it really comes down to the performance of the lens v. the quality of shot I received using the 100mm f/2.8L Macro.
Having said that, if I buy the 5dmkii, I will only have 400 left in reserves to get anything else. I really don't want to part with my 60d, but I know selling the used body for $650 (if I'm lucky) would then bump me back up to $1050 and again can buy another lens.
I've also considered a refurb 135mm f/2L direct from Canon. The best case scenario is if I buy one during their sales and I pay around $740. That would leave me with $860 and maybe I go ahead and dip my toe back into the 70-200's and get the f/4L IS. That would be $914, but I can get away with spending $55 over my budget.
I know there is a huge fight between those who prefer primes over zooms and I don't want to start one of those, but I've also considered a 300mm f/4L IS prime. But I read reviews that it is not good for panning and it is older technology from 2008 (which sounds silly) but I do have concerns shooting with a 300mm prime with limited IS on a crop sensor.
I've also considered a fisheye... but that's just for fun and is really low on my priority list.
So my question is... would an upgrade to the body with one additional lens (whether it is the 135mm f/2 or the 300mm f/4L IS or even the 70-200mm f/4L IS) be the best bang for my respective buck. Or should I stick with my 60D which has good low light performance (though not on par with the 5dmk ii or the 5dmk iii) and just get new lenses. It's not an easy decision.
OR is there something I'm not considering that would be an even better fit that I'm just completely ignorant about (and if someone mentions Nikon, I'll punch you in the face!).
Thanks for your help because I really have ambivalent feelings about both directions.