A good pre will make all the difference.

I have just dropped the thick end of 2K on an Avalon Vt373sp, for very good reason !

Even a dirt cheap Behringer channel strip (50 bucks off eBay) will be a massive improvement on your sound card. Even better if it can interface with your computer digitally though this will also depend on how good other A/D converters that you may have are. At the moment Im using MOTU 282 mk IIs (I have 2 of 'em which gives me 40 separate channels (16 being via Adat). I have to use the pres on the desk for 10 of 'em but that is not as biggy as they are dedicated drum channels.

In terms of placement there should be a sweet spot found by placing a mic (like an SM57) into the cone. If you keep the mic towards the top left of the cone right on the grill cloth you shouldn't be too far away.

You might also want to try a large diaphragm condenser, though you will have to watch you volume levels as it is possible to overload the capsule at high SPL. I have just got a AKG C414 BXLII for vox /guitar. Yummy ! However something like a Shure KMS series will also do a good job.
If you don't want to commit that much cash there are always the Behringer condensers. They do a reasonable impersonation and are good for getting a feel for what is possible.