Darkling,
Your PSU is not bad by any means, it's just not something that people would normally suggest. Too many people on Tom's have had PSU's go bad or blow-up in their face. We (collectively) are just looking out for your best interest. If your trust your PSU, that's all that matters.
For SSD's, reliability wins over speed any-day in my book. Out of the 4 you listed, here's what I suggest from top to bottom. personally, Intel is the best way to go if you want stability.
Intel 330
Muskin Chronos
Corsair Force GT
OCZ vertex 3.
I would shy away from the Corsair and OCZ as they use the new 2281 sandforce controller with 25nm nandflash, which has been having a world of issues and badluck follow it everywhere. 35nm nandflash does not have a problem currently. (example: vertex 3 max iops).
As I mentioned before, I am partial to nvidia videocards, but currently a 7950 is damn hard to beat, if not impossible price/performance/per watt wise. I don't think a 7870 would be enough of an upgrade for you. I would shoot for the 7950. Heck, spend an extra $10-20 bucks on a good OC version if you want. Just get something is 2GB or more of VRAM if you want it to last. Games of today and future games are making much more use of VRAM. If you can find a 4GB 7950 OC, then you have a winner!
The 7950 will not put any real strain on your PSU. However, anything more powerful will and a new PSU should be considered.
It's best to match RAM whenever possible. Another 2x2GB kit would be just fine. If you can't match the kit exactly, then just look for ram with the same voltage and timings of your current ram. If your not sure what that is, use an app like CPUid or SIW.exe to find out. If all else fails, just physically look at the stick. The voltage and timings should be listed on the side of the ram.
Let's fast forward for just a second. Let's say you get your additional ram, your SSD and say, a 7950 OC whatever. If you start having system reboots, random shutdowns, or game crashes, it's your PSU. You can verify by just putting your older 460 back in and if it's stable, then you need more power for your new videocard. However, if you get a sandforce based SSD 25nm, then it might be your SSD.
Here's the problem I see. It's possable that you get everything you want and it all goes very smooth and your very happy. (This is what we all want for you)
But it's more likely that you will run into weird issues or settings that you didn't account for before. And with that, new problems arise. You have a stable system right now as I understand it. Let's keep that stability in mind for just a second. Not enough power, a bad PSU, bad videocard drivers, buggy SSD, and new ram can all cause the exact same computer problems of random reboots or system hangs or game crashes. How do you ensure reliability and stability with your upgrades? How can you be sure what the problem is if any? here's how: Look below.
My advice? Follow these steps:
1. Get your ram and put it in your system in it's current state. Run a memtest for say 1 hour on all your ram. Maybe even run 3dmark06-11 to test your system. This will ensure that your ram is playing nice with the older sticks, ensure that enough voltage is getting to them, the correct timings are being used and are stable, and that your memory controller is not being stressed out because all of the banks are populated by ram.
2. Uninstall all your nvidia drivers, pull out your 460 and put in your new videocard. (Whatever your purchased) Test out a few games, run 3dmark again say 3-5 times in a row. If you have no crashes at this point, no bluescreens, and no random re-boots. (mostly rebooting during a game when the system is using the most power.), then so far so good. Your PSU will be enough to power your system and your ram/videocard addition are both perfectly stable.
3. Install your SSD. Put it on the sata2 port of your mobo and ensure that in your bios, AHCI mode is enabled for the controller/ports your using for your SSD. After windows is installed and all drivers are installed, do the following for SSD stability/reliability.
4. Disable pagefile, superfech, defrag, and indexing. These are SSD tweaks designed to help your SSD last longer and have just a touch more power on tap when needed. Now there are many more SSD tweaks that can/will help you, but those 4 are most important. The reason for these needed tweaks? All the optimizations that have been created over the years to help HDD's actually hinder/hurt SSD's. Go figure!
Anywho, take my advice and all others with a grain of salt, do a bit of digging with benchmarks/reviews about the parts we are all suggesting to you, and follow the steps I gave you and you should be a very happy guy!
I'll be monitoring this thread for the next 2-3 hours so that I can provide you with fairly immediate help. After that, gaming calls!
FYI: Any SSD you pick, go 3rd gen only, as the firmware/trim/controllers are much more optimized. sata2 vs sata 3 or not. just do it.