I'm not sure what you mean? If you have decided to get a PS3, then you have already made 95% of the decisions you will need to make! Your best bet is probably to keep an eye out in catalogs for PS3 sales and just jump on the next one that is bundled with a game you are interested in.
I wouldn't be surprised if there will be a Dust bundle, as they are aiming at the PC crowd a little.
Once you have got the console itself, you will need to buy a HDMI cable separately (or do they bundle one these days? They didn't for my 2 PS3s) if you have a HD TV to plug it in to. You could also decide if you want to buy a second controller, though I suspect that you won't need one of those if you are already talking about using a keyboard and mouse. I assume there is information out there suggesting that Dust supports those? I don't think any games supported keyboard and mouse for in-game controls.
Also, I'd recommend giving the controller a fair chance. I love my PC but kicking back in a beanbag or on a recliner for some console gaming is pretty good too.