SPCR

Hi there.

I am thinking of moving my setup from an Antec NSK2480 to something smaller.

Current hardware:

3-2105
mATX motherboard
2 x 4GB RAM
NSK2480
2 x SSDs (one for Windows, one for Linux)
Antec High Current Gamer 400W PSU

are there any really compact mATX cases that might accommodate all this?

The reality is that micro atx is not much smaller than ATX, its just 3 PCIe slot less, if you want to go smaller your best bet is to go into min itx, you will find a lot more option on cases for a smaller factor case there. That said if you want to do with your current hardware, i would suggest to look into

FC9 Alpha Fanless Chassis (you probably going the PSU from them).
[H]ardOCP Streacom FC9 Alpha Fanless Chassis Review

Silverstone GD06 (you probably can use your current psu).
TweakTown SilverStone Grandia Series GD06 HTPC Chassis Review

The Smallest matx case I know of is the cerberus. 18.5l tower case, versus your 25.9l horizontal case. Not sure it fits your space, not sure how quiet you can get it, and *really* not sure if you're willing to pay the price!