I'm not familiar with their QTCP, but the cost is suspiciously inexpensive. When dealing with machine tools and tooling, you sort of get what you pay for. I do know that many people use the Phase II QTCP, including myself. It's about twice the cost for a set at $300. Then there's Aloris (high end) at $800. So, my advice is to think about what it is you'll be doing and what quality you want to invest in and use. Better to buy it once than replace everything in the future. The G0602 uses AXA size QTCP.
I bought a smaller QTCP set for my first little Atlas lathe from Little Machine Shop and the handle broke off pretty quickly and I was always disappointed with it. When I sold the lathe I told the guy he can just have it... along with the old lantern style holder.
Definitely need a 1/2" chuck w/adapter, but there again, there are Chinese crap and better ones. I prefer Jacobs keyless for a good chuck that wont slip on you. Buy keyless and you'll never go back. Usually, the cheaper chucks round off the tightening teeth pretty quickly. Once that happens, a new chuck key won't bring it back.
For a live center, I prefer the double angle type. Sometimes you need that little bit extra extension and clearance on close work.
Several sizes of center drills, I use the smaller ones more often than a large one. You don't want a big'ol, deep hole in everything you'll be working on. Just enough to get a good surface to center on.
Measuring tools for sure. You'll probably use digital calipers for most work unless your fitting something to very close tolerances. This is where you can save some money. I have a couple of digital calipers from Harbor Freight (or most anywhere) that work just fine. You'll also be needing to mount an extra one if you want the tail sock to provide accurate depths. It wouldn't hurt to get a cheap dial indicator with mag base, although it's not something you'll use everyday.
Digital height indicator: Grizzly has the one I have. Not too expensive, but terrifically easy for setting your tool bit height is seconds. Most of the time, I leave mine set on center height, set it on the cross slide and adjust the tooling to match. Correct tool bit height is soooo important.
http://www.grizzly.com/products/0-6-Digital-Fractional-Height-Gauge/T21576?utm_campaign=zPage
DRO's - make this a priority to be a better machinist. Sure you can get by the old school way, but for quick-learning accuracy, DRO's are the way to go. I bought mine on Grizzy's site for fairly cheap. Easy to mount.
Some HSS bits, I prefer 1/4" and grind them myself. I also recommend a 5 piece set of 3/8" tri-carbides. You don't need 1/2" for most anything unless your hunkering down on some heavy cuts of steel. I got a drawer full of unused 1/2" tool bits.
Good T-handle allen/ hex-screw set(s) Metric and US/SAE.
As for modifications, be sure to check out mine on this link:
http://www.projectsinmetal.com/forum/general-discussion/diary-of-a-new-g0602/page-4/#p13336
I've been a G0602 Owner for 4 or 5 years now. You can make some really nice projects on this lathe. Low maintenance, never breaks down. Parts are available from Grizzly quick and cheap.
Rick