PC case fans help!!

So i'm using a high end rig for gaming, for the last year i've had the case open and its been fine, now though it gets too dusty so I wanna keep the case closed, I only have one fan though that works near the top left hand side of my case, it actually runs a lot cooler than before, question is do I need 2 case fans? cpu is down from 48°c to 38 and gpu from 58°c to 48, will this be ok? thanks!!

Other than that the only thing i'm thinking of is the HDD, RAM and MOBO temps.

Why would you have the case open for the past year? Case cooling is not based on not using the side panel, having it off totally disrupts air flow for the fans to do their jobs. You need an intake fan and an exhaust fan for best results.

Gets you better results than a closed case with no fans. Though even one fan and case closed will be better than no fan/one fan and the case open... Which TC experienced...

Don't use side case fans, 1 or two front intakes, rear exhaust is a must and optional if you have top exhaust as well

Why? because I thought an open case with no fans was better than 1 fan closed case, so it will be ok to use one fan? I do have another on top but the cable freyed.. so this should be ok? The temps are cooler I was just worried about RAM/mobo/HDD temps.

No it will not be ok if you use only 1 fan, I don't know what kind of GPU or CPU you're using but you'll fry them in summer for sure, or other parts as you're so worried about

get some cheap fan case as long as I can care but at least nothing will die there.

Again it's your computer do with it what you want.

GTX 670 and I5 3570k.. ok man i'll keep the case open until I get some fans.. works perfect in summer case open with good temps tbh.

It's not that good because this way it collects more dust and it got worse airflow if the case is open in the summer and no air is flowing.

Buy 1 or 2 simple 120mm fans. You should be able to place one or two in the front of the case. Either connect them to the mobo or psu through a molex converter.