I haven't personally tested this but....
I'm a PURP member and most of their coupons have "Coupon most be surrendered upon use" in the fine print, but this one doesn't. So I called my local GS and asked if I had two DSLs could I get two 3DSs for the $99.99. He told me as far as he knew the...
Just got off the phone with a GS manager. According to him, there is NOT a tiered system. I even called two different GS stores and got the same answer.
btw - I buy, sell, and flip video games and systems. The Ebay value of a DSL has dropped to around $45-$55 without games and extras.