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Are you asking something specific about "temporary" (i.e. for a year) connections or are you asking whether dual T1s with the equipment you've noted is sufficient?
If the former, unclear why "temporary" would make much of a technical difference. It might make a difference regarding contractional commitments.
If the latter, without knowing expected traffic volumes, unable to recommend whether your equipment is adequate, but a 3845 can easily handle dual T1s. It also supports an extensive QoS feature set.
For a LAN core the 3750 might or might not be fine; probably the former if there's only six other access switches. Again, though, without knowing what's the expected traffic, can't say this with much certainty. Also, there are many models of 3750s.