There's a couple of very good articles on fan configurations and fan comparisons that I'll send you as soon as I can dig them up. They're great references to have as you're building and configuring your system. If you want my two cents, the first thing I would do is make a list of components (I use pcpartpicker.com) that I plan to buy, tally up the power requirements, then pick out a good quality PSU that will cover it, with extra to allow for upgrades down the road like adding in a more powerful CPU, GPU, overclocking, or going SLI. Something in the 750W-860W range is about the sweet spot for most. That would be overkill for your current configuration, but would power a new high-speed CPU and a 770 or 780 nicely and still leave plenty of overhead. If you need 450W at full stretch, a 750W can provide it without stress or paying a heat penalty. With today's prices, the difference between good enough and great can be as little as $30. Just need to make sure that the sucker will fit in your current case and/or in a new case.
After that, the GPU, then CPU, etc. You'll also want to keep a close eye on compatibility, both with your current setup and with your projected one - a bad choice can create a roadblock down the road. Having a 780 TI is great...unless you can't power it. Or getting all the parts for an SLI setup, then realizing the mobo can't support it.
For the fans, unless you go with expensive ones like Noctuas, FLX fans are normally cheaper than PWM, and an all-PWM setup can be more complicated and require more parts (like PWM splitters) than otherwise. Great level of control available, though. I've built all-PWM, PWM on CPU cooler with FLX case fans, and FLX-only - I prefer the first two because I tweak the settings a lot (I spend more time tweaking fans than playing games), but an FLX setup can be every bit as effective at cooling, and is usually cheaper. FLX fans can be controlled through the mobo, an integral case fan controller if the case comes with one, or an aftermarket fan controller.
There are lots of variables to consider with the fans, with volume of air moved (measured in cubic feet per minute, CFM, or in cubic meters per hour, m3/h) usually being the first consideration. Size is another - larger fans tend to move more air, or can move an amount similar to a smaller fan but at a lower RPM and noise level. Noise levels are yet another - how much noise can you tolerate? Different fans will have different noise levels and qualities at different settings. If you have a small high-rpm fan, it may provide great cooling but create a buzz that makes you want to shoot it. Also, fans can be optimized for specific purposes like for use on radiators or heat sinks. Many considerations. You'll have to decide, at least in general, what your needs and preferences are, then find fans that fit. There are plenty of folks here at Tom's that will help you do that when you're ready.