Equinox Tarp is a good idea - bugs will really bother you in a tarp come summer though - try to find an MSR Hubba on e-bay or something - they retail for $250 or so - I skip the ground cloth for tyvek - here is a link to one - good luck
cgi.ebay.com/MSR-Hubba-Tent-/300531585892?pt=LH_DefaultDomain_0&hash=item45f914 1364#ht_547wt_1141