Performance (40% of the final score) - with voltage regulation rivaling a good independently regulated unit and extremely low ripple and noise results, this is a hard unit to hate. That said, I would like to see capacitors on the secondary side that are a bit better quality to insure this unit has a long and healthy lifespan. As it stands right now, this is a very good unit that stops a little bit short of being the best unit it can be. As such, I'll bestow a 9 on it for performance.
Functionality (20% of the final score) - this one's a little tricky. On one hand, I usually like to see a good amount of connectors, and at least one 4+4 pin modular EPS12V/ATX12V connector. But, on the other hand, this is a specialized unit meant for a specialized form factor. You're not going to want eleventy gazillion Molex connectors if it means hiding them in a box the size of a stack of books. I'm going to take a couple points off here, however, because there are MATX boards out there with EPS12V connectors. Also, I do feel that even these smallish units could benefit from some cable sleeving. 8.
Value (30% of the final score) - EWorldSale is listing this unit for $43.00. At that same vendor, there is only one other unit in this form factor, an Inwin unit for $32. Given the limited competition for this unit, I think it's pretty safe to say that if you need a unit like this, the Seasonic unit makes for a terrific value. 10.
Aesthetics (10% of the final score) - as bland as the day is long, this unit just isn't what I'd call a real looker of a unit. It's just not attractive, at all. It's gray, the cables aren't sleeved, it has a stamped fan grille... there's nothing more to say about it. But the load table sticker... uh... kind of looks ok. 4.
Performance
9
Functionality
8
Value
10
Aesthetics
4
Total Score
8.5
Summary
Bland on the outside but spicy on the inside, the Seasonic SS-300TFX is a small form factor unit worthy of some serious consideration if you happen to have a case that requires such a pipsqueak of a unit. It's efficient, it's quiet, and it's extremely stable with its voltage regulation. I do have some small objections over the quality of the secondary side capacitors, but currently we can't really be that picky with units like this. There just isn't much demand, and thus not much competition, for this unit.
The Good:
efficient
extremely good voltage regulation
quiet
The Bad:
secondary side capacitors are questionable quality
