Yes, you should.
Anyway, all sparky iso images features "testing" repos instead od "jessie" so there is no change needed.
Looks like you changed it to "jessie"?
With an interest in shedding a little more light on the situation, I just checked my Synaptic Repository listings and both Testing and Jessie Repository listings are listed, as well as a PlayonLinux.com listing for Squeeze. (This on my Sparky Ultra Openbox).
Which makes me think that neither Galen nor Pavroo is "stubborn" but rather "committed" to getting Galen's Sparky Gameover installation working - in fact, that's very clear, and is a very positive thing - for all Sparky users.
Another thing: LMDE GAVE UP on Debian Testing (and offers far fewer desktop environments than Sparky). This clearly demonstrates that both Pavroo's competence and committment are what make Sparky the best Debian Testing derivative available.