Not sure which ION USB turntable you have now, but the first thing that comes to mind is the damage it might do to your valuable LPs. I don't think there's much disagreement that some of today's inexpensive record players are torture devices for vinyl.
Secondly, I think money spent on source is money well spent; garbage in/garbage out. Start with a quality source and work on the quality of the downstream electronics after. (speakers being the second thing to get right)
The Technics SL-1200 is a sure bet. As others have said, it has 40 years of history and in that time has proven to be a reliable workhorse capable of fine performance. It's also a safe bet financially as it will almost certainly increase in value. (They stopped making them last year)
$350 is a good common price for an SL-1200 MKII in good shape. You could pull the trigger on that purchase feeling confident. I would strongly recommend getting one that has never seen DJ use. That kind of hard use can wreak havoc on the all-important tonearm bearings. Any slop in those bearings is going to degrade the performance of whatever cartridge you mount on it.
I'd also suggest you get an MKII or better. The earlier ones are certainly cheaper, but I think the improvements to the MKIIs are worth the initial cost.
I've heard good things about the TCC preamps. Other options to consider would be the first-generation Musical Fidelity V-LPS which can be had for $99, sounds awesome and can handle low output moving coil cartridges if you ever want to try one of those in the future.
(EDIT TO ADD: I just looked on Amazon and it looks like the days of the $99 M.F. V-LPS may be over.)
Also for $100, you could get a used Cambridge Audio 640p. Plenty of info about those on the web.
But what I would most strongly recommend is an ART DJ II phono amp; it's about $50 and has excellent sound and adjustability. Not sure in my experience that it's all that different sounding from the Musical Fidelity.
http://www.amazon.com/ART-II-Preamplifier-Outputs-Switchable/dp/B000AJR482/ref=sr_1_1?ie=UTF8&qid=1334165440&sr=8-1
(FWIW, I either own or have owned all these phono amps except the TCC)
The Shure cartridge is also a safe bet. Although keep in mind that Shure cartridges are generally liked by folks who prefer a warmer, softer presentation. An equally well regarded cartridge that gives a bit more of an open, detailed presentation would be an Audio Technica AT120E, or for a little more money, an AT440MLa. And really, you can't go wrong with either the Shure or AT for a first high quality set up.
Amazon.com: Audio Technica AT120E/T Standard Mount Phono Cartridge: Musical Instruments
Most of all, have fun and let us know how it goes.