i wouldn't trust a 2x4 (possibly the very straight expensive good quality ones), i'd do PVAudio and what I've said and thats a 4 foot or 8 foot aluminum ruler...
k12ug, although i see this as a very good and cheap alternative to having just a ruler and some clamps, in the long run, i honestly believe the table saw will win out...
for example, for cutting the front, sides, ports inside and back and back piece, once you have your fence set on the table saw, just slide each piece in and rip, rip, rip...for this jig, you have to measure each time you rip and make sure its exactly on and even still it might not be perfect like a table saw...
so if you're just building a couple boxes a year max, i say this jig will be fine, but if you're planning on building alot of boxes in the future, i say the table saw will save plenty of time to be worth the $150-$200...
btw you can get a nice JET belt driven table saw from
amazon or mendards for $230...