Grex is not a TBC, and has many side effects, the worst being similar to a bad AGC. The only time that I've found a Grex useful is when removing known copy protection between DVD recorders. So DVD recorder analog out > Grex > analog in to another recorder or capture card. That's because some PITA recorders prevent easy copying of programs, either burned to disc or simply re-captured. For that, the Grex helps. But for analog tapes, forget it, crap.
Those "video stabilizer" boxes were just a nonsense device sold to gullible suckers in the 90s. It does almost nothing, the reason it costs almost nothing. And honestly, it's worth $0.
There are no external lines TBCs. However, a Panasonic ES10 or ES15 comes close. It'll still choke on copy protection, and some other errors, but it can salvage excellent quality (signal quality, not necessarily visual) homemade tapes. Though it should improve quality some.
An external framesync TBC is not a line TBC. Line TBCs are generally found in S-VHS VCRs.
An external TBC is the only guaranteed way to remove copy protection. (Excluding DVDHDD>digital, where the Grex is better, oddly enough.)
My advice? Get that ES15 for about $100
Here's one: http://rover.ebay.com/rover/1/711-53...m/123680094723
But be warned!!! eBay
sellers are notoriously bad for lying about quality, "forgetting" to mention problems/defects, and for pathetic padding-less shipping. You may end up with a box full of busted plastic and metal (due to zero padding) that smells like an ashtray. I'm not exaggerating, that is exactly what happens, and often. But if you want cheap, under $100, you're in gambling territory. Trying to save 100 bucks may end up costing 100 hours in grief.