Path 1 - change that to a 3570k.
This will help with the video converting (forgot its proper name) due to Lucid Logic Virtu which can use the integrated graphics to assist here. As well as being a stronger CPU as well.
Changing the mobo is pointless, and will incur the cost of a new OS (probably). The 7870 and 8150 will increase your gaming and conversion performance.
This will increase your gaming performance by a lot. No point Crossfiring (SLI is Nvidia cards) if you are playing on a single screen.
Of all the options, think Path 1 is the best. Simply because it gives the greatest flexibility in what you can do later. Wouldnt advise getting another 560Ti though.
lol, didn't realize I wrote SLI for the AMD card, thanks for the reality check .. the 3570k isn't a bad move budget wise since it is only $20 more, but (Speaking as a long time AMD fan) .. I have read so many good things about the 2500k/2600k's in the matter of gaming performance.
When I talk about video conversion, it's not my top priority. It's more turning digital files into DVD's once in a while for family. It's mostly movies and gaming. Right now in my Skyrim addiction I am at an avg of about 30 to 40 fps, but getting annoyed with bottlenecks
The 3570k is the Ivy Bridge upgrade of the 2500k (Sandy Bridge), and comes with the typical Ivy benefits (lower power draw, PCI-3, ~10% better performance). Pretty much all the traits of the 2500k are in the 3570k.
In that case a processor upgrade isnt really needed. Maybe go with the 7970, and if you want to upgrade the CPU later, the FX-8350 which should be releasing sometime soon. That way you dont need a new mobo.
And here I was thinking and gave up and was sticking the the a10 series, I didn't even know they were still working on the Fx chips... ill stick with going for a 7970. However I was looking at the 7870 frozer hawk