Being in more or less the same situation as you (although my Q9450 has yet to croak), I'd get the i5 for longevity's sake. If you can see yourself getting a cheap/used quad (or even an i7) in a few years time, then the i3 is a decent stopgap (with good performance for its price), but considering the tendency for applications and games to multithread ever more efficiently, getting a true QC seems like the best bet for future proofing. I doubt anyone these days gets more than half-decent performance out of a 6-7-year-old E8400 gaming rig, while I'm having no real issues with mine (Q9450+HD 6950). Sure, it's more expensive today, but worth it down the line.
How much did you pay for the motherboard, by the way? Around $100, judging by your post? Since you're not OC'ing, I'd really recommend going with the bare essentials there, and choose a quality brand over "might be useful some day" features. Just taking a quick look at newegg.ca, I found a decent looking Gigabyte H81 mobo for CAD $80 and Geil/G.Skill 2x4GB DDR3-1600 C9 kits for around $70, leaving you $250 out of your $400 budget. Sure, the motherboard only has 2 SATA3 ports, but that only matters if you plan on running more than 2 SSDs at some point, HDDs never even saturate SATA2. Same goes for lack of PCIe x16 slots - from what you're saying, you'll never be doing CrossFire. Z97 only really makes sense if you're overclocking, otherwise you're paying for loads of features you'll never use. And since you're saying "the less I spend, the better I will feel," those $20 for the mobo seem like a decent way of saving a bit. Are you able to return the Z97 board? Otherwise you might be able to sell it off?