I haven't done a full build since '07 so many things have changed, and I'm trying to bring myself up to speed.

Is it possible to make a fanless/passive PC with a bit of horsepower for games?

Considering:
Fanless PSU
SSD
Fanless GPU AMD 7750HD / R7 250 ? NVIDIA GT640?
i3 / i5? Maybe i3-4130T? - Is the nofan CR-95C the only possible passive heatsink?
Appropriate Case (probably atx) / RAM

Is this doable or advisable? Would the ambient heat of all the parts be too much without a case fan? Would the cost / performance be acceptable?

Any thoughts would be appreciated.

Doable yes. Practical, probably not. In a normal gaming system you might as well go with a couple of fans and it can still be very quiet. You also get more performance for your money if you optimize for reasonable quiet performance rather than complete silence in a gaming system.

+1

Better off to figure out how good of a gaming machine you want and then optimize for noise. A decent gaming build will be damn quiet at idle/non-gaming loads. I wouldn't build a dual core gaming PC these days. Use this article for some inspiration.

I agree with vicotnik, its doable, but its not efficient, at least for somone looking for a gaming build.

The difference that very little air moment is huge, its best imo to get good fans that you can drive them to inaudible levels than to plan a full gaming fanless build. Today you can make fans like Noctua NF-A14/15 go into 200rpms with pure bios, you can drop fans like Antec True quiet 140s to 200rpms or so in FanXpert2, there are much better options on fans today than there were 5 years ago, and Intel lastest cpu/chipset, Haswell..... run very hot, so trying to go for a good performing gaming build and fanless.... you will have to cripple yourself too much, imo not worth it when there are very good choices in gpus, psu, fans, that have fans but run relatively quiet.

Heatsink cases are another option for going passive. Here's a very good example from this forum in a Streacom FC5 with some pretty powerful components:
viewtopic.php?f=14&t=65463

The PSU is external in that example as an ATX PSU was required to power everything. If anything it's far more powerful than what you are proposing. The newer FC10 would raise the cooling capacity and is larger.

There is also the forthcoming Streacom DB4 but at this point there is no final product out so I suggest you just Google for it and see what comes up in addition to this thread where a Streacom rep gives us some info about the PSU:
viewtopic.php?t=66632p=578624

Reviews indicate that a passive 7750 will not survive any prolonged gaming action without a case fan.

If you try and go for something less powerful than a 7750, you end up noticing that Haswell HD integrated graphics chomps over all weaker GPU cgards.

The only "real" passive heatsink is IMHO the NoFan one: any other cooler is just sub-par and strongerly depends of case airflow.
Otherwise, something like a Scythe Mugen 4 with a pair of 2-300rpm fans would go fine temperature-wise, with no practical noise-penalty. With no hot CPU, even something like a Cooler Master 412S should work, provided it's fan-swapped. Obviously you need a fan speed control system, either software or hardware.

With reference to the CPU, if you go for a dual core, IMVHO I would not look for any -T part number: nothing more than a G3220 would be more cost effective, and you could also delid and lapping it without worries.

There is also no need for a fanless PSU, IMHO: a semi-fanless, such as a Corsair RM 450, would work good and let you spare some bucks.

About the videocard, IME either an ASUS GTX-650Ti DC-II OC 1Gb or a MSI N650-TI OC 1GB Power Edition would be practically inaudible and will give you much more horsepower than any passive 7750 and the likes (usually for not so much more money).

Eventually, for case and SSD there's plenty of options: my current favourites are Corsair Neutron GTX as SSD, while for the enclosure, even if there are probably safer bets (Fractal and the likes), maybe I would give a look to the new Antec P100 (anyway, with reference to any case, you should check the compatibility if you go for the NoFan cooler).

Thanks for all the great insight guys! This forum rocks!

I think I will refocus on a decent quiet machine and not a completely passive one. Using the case as a heatsink is interesting, but a bit more involved than I currently want. Maybe in another 6 years passive gaming PC's will be common.

I will probably buys some parts after the holiday, I will report back and let you guys know my build.

Thanks,
frankd

I would look for a case on http://www.hd-plex.com/ . I researched the Streacom cases and especially the Streacom FC8 has its challenges assembling it.