If it has a Sandy Bridge Pentium dual core 2.8GHz processor, then it's probably the Pentium G640 (which only supports DDR3-1066 memory). The HP 6300 is less likely to have the Pentium G840 (which also supports DDR3-1333 memory). The listing doesn't say what kind of memory it has, but it's possible that it could be equipped with DDR3-1600 (limited to whatever speed the processor supports). NewEgg's site claims it has Intel HD 2000 graphics, but that's not correct. The Sandy Bridge Pentiums were limited to "Intel HD Graphics" which has 6 Execution Units just like the Intel HD 2000, but it lacks Intel Quick Sync Video, InTru3D, Intel Clear Video, and a couple of other features. It's less powerful than a Sandy Bridge Core i3, if that makes a difference to anyone at this price.
On the other hand, the specs I've seen for the HP 6300 SFF say it has the Intel Q75 Express chipset. It's too bad the listing isn't clear about that. But if that's the case, it should have some USB 3.0 ports and you could upgrade to a decent Ivy Bridge processor (the Core i3-3225 with Intel HD 4000 graphics or a Core i5-3470, for instance). But then you might want to upgrade to DDR3-1600 memory if it doesn't already have it, and heck, make it 8GB, and what about a GeForce GT 1030... Then it might turn into a money pit, ha ha.
My own rig is a Core i5-3475 and MSI H77MA-G43 with 8GB DDR3-1600 CL9 memory, two Seagate hybrid drives, an Asus sound card, a GeForce GTX 1050 and Windows 7 Professional, which is only a few steps away from this basic computer... In other words, the foundation is pretty much the same (Intel H77 chipset and Windows 7); the difference is in the peripherals I added to it. The money pit factor.