The R9 270X is more powerful than a PS4 GPU, but the PS4 GPU has that extra VRAM to throw around, which'll help with unique optimization later in the life cycle of the PS4. What Leonell said is also correct, to an extent, but it doesn't make quite that big of a difference, since multiplatform PS4 games already lack just about as much optimization as typical PC games.
Overall, the R9 270X should manage better graphics and framerates than most PS4 games, barring a couple exclusives, like whatever Killzone game comes next.
The FX-6300 should hold up well enough in games using 6 cores, as the PS4 CPU is weaker. However, you can bet every PS4 exclusive and well developed multiplat is going to code their games to make use of every bit of...