I would say go for an internal drive, preferably, from Seagate (2TB or less) and then buy any enclosure. Since speed is not an issue for you, you can settle for USB2.0 enclosures, they are cheaper than USB3.0 enclosures. That would certainly take care of VFM aspect of your requirement.
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1.IMHO, get a new one. It is always safer.
2.For <6k, you wouldn't be getting any of Intel's latest offering(Haswell). Given that here you are literally forced to consider an upgrade, that shouldn't be a problem. Anything that you buy which costs less than 17k (10k for CPU and 6.6k for Mobo)...