Cooling multi GPU configs [THEORETICAL]

Many Crossfire R9 290X and R9 290 owners bought the refrence blower cooler because "it gets better temps in crossfire". This is completely wrong. The refrence R9 290X hits 93C on the uber fan profile when on it's own. So if you put a another heat source bellow it it will hit 95C and have serious issues staying cool regardless of the fact that said heatsource is not dumping the majority of it's heat in the case because the R9 290X above it only has a 2C margin for warmer intake air.
The back of an R9 290/R9 290X gets stupid hot especially the VRM section which is also closest to the intake fan of the card above it. This results in the following happening:

With non reference coolers that dump the used air back into the case this is not an issue because the cards is operating around the 75C range when alone. This gives the non reference card a +20C allowance on intake air before it hits the same temp as the reference design.

Non refrence coolers also have about 2 to 4 times more air passing through their finstacks making the output air of a custom cooler rather cool typically in the 30-40C range depending on load and clocks. Now assuming your case has fresh air going to all areas at all times the 40C exhaust will be mixed with the cool outside air meaning that the top card will at worst be getting air in the 35C range meaning it will hit the 90s. This would look something like the image bellow:

Now I would like to remind you that this is purely theoretical and based on information from around the internet and my experience with my windforce cards. However if anyone is willing to ship me a pair of R9 290X reference coolers I have all the equipment to do full testing of this. If you can ship me a pair of R9 290/R9 290 reference coolers just leave a comment.

Another thing to note is that this only truly applies to really high power draw cards because the blower coolers do in fact keep in case temps lower than radial fan designs just this difference is not big enough to keep 93C cards from hitting 95+C.

Case Review: Xigmatek Alfar

Price:
   The  Xigmatek Alfar is an ATX case and cost ~1150CZK (~57.5$) after 21% VAT.

Features:
   - ATX motherboard
   - 2 front panel USB 3.0 ports and audio in/out jacks
   - 3 5.25" bays
   - 4 3.25" bays
   - 3 2.25" bays
   - Supports 180mm PSUs
   - 6 PCI-e expansion cards can be up to 300mm long
   - 1 PCI-e expansion card can be 260mm long
   - Supports 160mm coolers according to spec but I would stick to 158mm because some 160mm
   coolers don't actually fit
   - Fan Support:
       2 120/140mm fans in the top without proper radiator support internally
       2 120/140mm fans on the side panel
       2 120mm fans in the front with no radiator support
       1 120mm fan in the back supports a radiator
       1 120mm fan in the bottom of the case
   - Tool less installation of 2.25" 3.5" 5.25" drives
   -Watercooling tubing cutouts

Build Quality:
The entire case is painted black with the outside painted in a "rough" finish that resist fingerprints and the inside an almost sooth finish. The front cover is plastic and has a rubberized coating which to is fingerprint resistant. The whole case is built of steel but is surprisingly light making it very easy to carry even with a full system inside. The case is very rigid for it's weight with very little flex to the side panels. The only major flaw this case has are the plastic feet that do not grip surfaces and make it very easy to slide the case around.
It also has a distinct cheap rattle to it.

Building in the case:
Was very easy. There is plenty of cable management room behind the motherboard tray and there enough and big enough cutouts to cable manage even a dual GPU system. The biggest issue occur above the mother board with the top fan mount and my massive Phanteks Heatsink (review) because the heatsink blocks access to both fan headers and fan mounts. Cable management was harder to do than in some larger cases but still much better than other similarly priced cases.

Summary:
My go to case at this price point.