I think that you are too worried about the filtration, after all you don't use your evo in gravel!
I think that an induction kit is really better than the standard airbox, maybe it will not make a big bhp improvement over the ralliart panel filter with the relocation kit, but for the price it will have a better look, quality, noise and it will be easely cleanable. I wouldn't pay something like 85£ for a panel filter and 350£ for a relocation kit, when you can have the hks rs kit with the alloy piping, silicone hoses, and filter for 300£!
The apex i kit is ok but I don't think is really better than the others and it looks small.
About the hks, I think that the filtration should be good, it's the foam that is used in motocross bikes and they should filtrate dust!
Also with the BLITZ or the apexi you keep the standard plastic piping, and if you want to replace it you have to buy an expensive relocation kit from ralliart or cusco.
Have a look at rallytech for their wrc carbon airbox or at monster that have a small carbon airbox with relocation kit.
About the VTA blow off valve, probably the hks is the best one, but I think that you should fit an induction kit before buying it and you will notice that it will make the same noise with the standard valve without spending 250£ and having idle problems. If you really want to upgrade it buy a forge recirculating one.
With that money you can buy someting better for your exhaust or a boost controller.