1st Gen to 3rd Gen
If you are looking to do heavy graphics would, I would absolutely recommend picking up any IVB i7, due not only to the performance increase which will range around 30-40-50% depending on your application, but also to the price, which will most likely be dropping around Christmas time by a pretty nice amount. I remember during Black Friday I saw a 2600k for 250$ -- very good deal.
The thing about Haswell is that the new line of CPUs will be more aimed at decreasing power-draw than sky-rocketing performance. Despite the new 22nm process, Ivy Bridge's core architecture is not manufactured to take full advantage of the smaller processor fabrication -- For the most part it is identical to Sandy Bridge. Haswell will stay on the same 22nm node, but will feature a core architecture optimized to take full advantage of 22nm, which means stable performance whilst consuming much less power. Haswell represents a significant investment by Intel into the mobile market, and the desktop CPUs have more or less taken a back seat thus far.
Nevertheless, I really do think the 3770k will not disappoint. As far as OCing goes, IVB is notorious for being fairly poor overclockers, due to the thermal compound they used instead of soldering, and that translated to a typical spike in temps after surpassing a certain voltage level, or core clock. Right now, a 4.5GHz IVB overclock would be considered pretty good - unlike Sandy Bridge which could go much farther. Push IVB past 4.6 and 4.7, and you will see a dramatic increase in temps. Now, I understand you will most likely not need a 4.7GHz overclock, so I wouldn't stress out about this too much.
If you are not looking to overclock, however, you can save a few bucks by opting to go for a 3770 without the "k", which implies the CPU cannot really overclock, but will cost less.
The gaming performance when moving to IVB will likely vary depending on what game you are playing. BF3, for example, is one of the very few games that takes advantage of virtually every resource you throw at it, so will certainly see improvements there. Another game is Skyrim, which is known to be very CPU-dependant. There will be other games like DiRT 3, however, that will shoot up in frames with a GPU upgrade, regardless of CPU power. It really just depends
Motherboard
Motherboards are rated on more than just the amounts of ports they have. One thing you should take into consideration is the VRM, which is a bit too off for me to fully explain here. You mentioned that you have 6 different storage drives?
I think that this MOBO would be ideal --
Gigabyte Z77X-D3H - I actually purcahsed this on Black Friday for my build, and I am very satisfied with it. It has a total of four SATA II ports and four SATA III ports, giving you an extra two SATA ports for whatever you need. It can work with SLI configurations in case you ever wanna upgrade to dual 670s in the future, and VRM is quite good.
You can go with the Maximus but understand that those boards are meant for high end overlocking/Dual-GPU configs. You won't really see much of the performance increase and you will be facing dimishing returns for the most parts. You don't need to spend over 150$ on a MOBO with your needs.
As far as PCIE -- the differences are pretty negligible if you using any single card, period. It's just more band-with
Anything I didn't cover?