The Tewksbury shop is ok, but they are admittedly thin on Basketball cards.
The Salem, NH shop I sent you (Chris's Cards & Comics) has a pretty great selection of packs/boxes/singles.
I used to collect basketball and have a pretty big collection, but I'm slowly moving more towards baseball and football (can't collect everything). If you have anything in particular you collect from basketball, let me know!
Also, the Greater Boston Sports Collectors Club (gbscc.com) is a cool group and meets once a month in Woburn. I'll probably be there this coming month's meeting (Oct.) if you want to meet up there.
My website: http://www.thesportscardguy.com/ (w/blog, want & trade lists & TTM successes)