Really depends on your budget and if you are going to OC it alot.
Although most people will just say "go air" the advantage of a great watercooling system is huge.
For one,even if you OC mildly you will be keeping the CPU and GPU really cold which increases their lifespan.
Another cool thing is that after you get the WC system going it can last for years and years,even if you redo your system all you need is the cpu/gpu/mobo blocks and you are ready to go.
Of course WC has downsides:if you have no idea what you are doing you can blow the system off or actually getting very dissapointing results.There is the leak problem also that can damage the system and the dreaded system start even if the pump is not working.Also power consumption is higher(as I heard).
If money is not an issue i'd look into WC setups made by TW users and try to understand the concepts and risks behind it.
So to sum it all up:
-WC has great potencial in cooling but carries risks and it requires knowledge of WC components to make it work.
-Air is for 90% of people around TW enough.It is safer and easy to get going.
Lastly dont get into cheap WC systems,especially closed loop systems that cannot be upgraded.These are much more expensive than a air solution and do not preform that better,as in its a waste.
Some kits are actually good and advised for WC noobies.
Check the WC section sticky to learn more and decide for yourself.
Yeah that's right , if you're not overclocking your system then you'll be fine with everything you're running now. If you want better temperatures I'd say get a cheap after-market cpu cooler such as the Evo 212+
Also for where you should put your PC ? Somewhere well ventilated , my PC is currently on my desk where there's loads of space for ventilation. Try not to put it in a cupboard where air is restricted.