XPS 8900 case cooling and custom fan configuration

After the GPU and PSU upgrade I did on the XPS 8900 I am now in the mission of getting the PC case cool down under heavy GTX 980ti load. My current setup right now follows:

1. Rear case fan as exhaust using BGEARS B-PWM 90 (88cfm) which is connected to the motherboard (does not run full as the motherboard controls the voltage and no way it can be controlled by the user).

2. Stock dell case fan running at 100% as intake at the front of the case (noisy).

Room ambient temperature is around 20-21°C. and the PC is literally besides a window. If the GPU is under heavy load and running 15 minutes I get 69-70°C (with custom fan curve) but the rear case fan will not push out the hot air as planned as it is controlled by the Dell motherboard. I get max of 72-78°C on 4 cores of the CPU while the GPU is under full load.

Now if I open the window a few inches 8°C (depending on Canadian winter temp but it hovers like that during day time) I get to drop the GPU temp to 65-66°C and the GPU fans will rarely kicks in and CPU temps drops to 55-65° under load. I also saw the temperatur of the SSD and HDD go down by 5°C. I know the cool air coming from the intake helps a lot but I want to find a solution that I won't change the case and won't open the windows so I decided to buy the following:

- Titan adj. dual fan PCU slot VGA cooler

- Noctua 92mm NF-B9 PWM fan

- Evercool Twister Fan Speed Controller PCI Slot or 3.5"

- Rosewill 2.5-Inch SSD/HDD Mounting Kit for 3.5-Inch Drive Bay w/60mm Fan RDRD-11003

The plan is put the Titan fan below the GPU to literally quiet down the ASUS GTX 980 ti fans and add intake as the bottom side of the XPS case is perforated which is a perfect spot to have intake. Then replace the stock dell fan that I reused for front intake with the Noctua fan to quiet it down then have it connected to the motherboard to not have any fan errors. The BGEARS rear exhaust fan will then be connected to the Fan speed controller which I will place on the 3.5" bay (the knob will clear the drive cover). The idea is I want to manually control the speed of the Exhaust so that when I am using the GPU at full load I can turn it up to full speed to be able to use the 88 CFM for exhaust. 

My understanding is that if I keep the exhaust BGEARS at low to mid settings (40CFM) and have the intake Titan fan at mid seetings (33 CFM) and intake Noctua fan controlled by the Dell board at 30%-assuming (11 CFM) I will have Positive cooling which a lot of people do like to keep dust out. This setting will be used while not using the GPU too much (idle at 44-48°C).

Then when I use the GPU I will crank up the exhaust BGEARS fan to 100% to have NEGATIVE pressure (assuming the dell modo will crank up the voltage for the front fan to 100% (which I doubt it will) for best removal of heat inside the case.

Is that setup better or should I do it this way (full positive setup):

- Noctua fan as exhaust and controlled by Dell mobo most likely won't run more than 30CFM

- Bgears as front intake and controlled by the fan controller (can be 30-88CFM if needed)

- Titan running at 50% or even at 100% all the time. 

The positive setup will have 154 CFM at max coming in to the case and the Bgears fan will be noisy but I do not care as whenever I render my animation I usually step away from my machine as it will take at least 20 min. to hours anyway. One other thing is that I will be putting a filter (stockings) on the intakes-will have to be creative on the side perforations) to filter dust somehow.

Any input will be greatly appreciated and please do not tell me to get a new case as I do not want to do that and I want to keep the small form factor of the XPS case. 

Thanks!