You are not buying a camera. You are not buying megapixels, ISOs, autofocus points or even video recording. Buying an SLR is buying into a system and this is the biggest change from shopping for a compact.
Lenses are more important than the camera. Your camera takes no images without a lens painting one upon the sensor. Lenses determine the subject matter you can shoot and the conditions where/when you can shoot. Everything you do with the camera passes through the lens first.
Tripods are more important than the camera. The camera needs a stable platform, whether shooting still lifes in a studio, a grain of rice blown to more than life size, landscapes at dawn, birds in detail at 100 meters, stars under a clear sky or making mist out of moving water. Long shutter speeds, long focal lengths and the highest sharpness possible all require that camera movement be eliminated, stability that the human body simply cannot provide for more than a fraction of a second. Image stabilization helps at the borderline, but will not help past a second. A blurry photo is beyond saving.
Flashes and lighting are more important than the camera. ISO is no substitute for good light. Sometimes the light simply sucks and it is easier to just bring your own. Photoshop takes expertise and labor to do its magic. A homemade light tent and pair of 60W bulbs will do more for your eBay photos than an any SLR ever could. Learning how to manipulate the light is as important as learning how to shoot in every condition.
The camera body is a part of a system. It is an important part, but still only one part. Do not neglect the rest of the system, especially when starting from scratch with a limited budget. If you end up doing an hour of Photoshop to fix each photo, you may as well have stuck to a compact. Getting great results straight from the camera is a tricky and rewarding skill that requires a team effort from your whole system. Lenses especially should not be neglected, for they are the real core of an SLR system.
Stop thinking about camera specs. This works somewhat for compacts, but for SLRs it is an expensive distraction from more important issues. The camera cannot and will not do it all.