I would think very carefully about buying that phone from Ebay.
First, you haven't provided a link so we can't see who you're buying it from. Is it from a domestic US dealer with a good reputation, or someone from China? Does it have a US warranty? It may not, being an international unlocked version, so if anything goes wrong with it you may be out of luck and that will cost you a lot more than the $100 or so you saved by not buying the official Metro version.
If you buy a version that does not support the same bands as the 920T you may be disappointed in the results depending on how solid the supported bands are in your service area. I'm in a major city with good LTE service and I still find my phone frequently switches to 4G/HSPA. This isn't a problem with a phone that has those bands as it's still fast but without those bands your data would either get very slow or drop out altogether if you lost the LTE signal.
Finally note that the Metro/T-Mo versions of the phone (or any of the current phones they sell) will include native WiFi calling which is a very useful feature. Other versions of the same phone, even if 100% compatible with the right bands, will not have this feature and it is not possible to add it later (not even by rooting, AFAIK there are no custom ROMs that include it).
So please bear all of the above in mind when making your purchase and think whether the lower up-front cost is really a good deal. If paying the full price is a problem for you perhaps you may want to consider the S5 or even the S4 which are still perfectly good and up-to-date phones. You can still get a brand-new S5 from Metro for much less than the S6 and don't forget about the removable battery and SD card slot which the S6 doesn't have (don't know if those things are important to you but they are to some people).
First, you haven't provided a link so we can't see who you're buying it from. Is it from a domestic US dealer with a good reputation, or someone from China? Does it have a US warranty? It may not, being an international unlocked version, so if anything goes wrong with it you may be out of luck and that will cost you a lot more than the $100 or so you saved by not buying the official Metro version.
If you buy a version that does not support the same bands as the 920T you may be disappointed in the results depending on how solid the supported bands are in your service area. I'm in a major city with good LTE service and I still find my phone frequently switches to 4G/HSPA. This isn't a problem with a phone that has those bands as it's still fast but without those bands your data would either get very slow or drop out altogether if you lost the LTE signal.
Finally note that the Metro/T-Mo versions of the phone (or any of the current phones they sell) will include native WiFi calling which is a very useful feature. Other versions of the same phone, even if 100% compatible with the right bands, will not have this feature and it is not possible to add it later (not even by rooting, AFAIK there are no custom ROMs that include it).
So please bear all of the above in mind when making your purchase and think whether the lower up-front cost is really a good deal. If paying the full price is a problem for you perhaps you may want to consider the S5 or even the S4 which are still perfectly good and up-to-date phones. You can still get a brand-new S5 from Metro for much less than the S6 and don't forget about the removable battery and SD card slot which the S6 doesn't have (don't know if those things are important to you but they are to some people).
