Since budget is your primary concern, I would look on the gear swap forums on here, WhiteBlaze and BPL, as well as Ebay and Craigslist for great deals on used gear.

Another option is to find an outfitter that you can rent gear from, just to give you an idea of what works for you.

If my budget for all three was $275, then this is what I would purchase:

- 8x10 Tarp: $70
http://www.campmor.com/outdoor/gear/Product___20069
- Campmor's +20 degree sleeping bag: $120
http://www.campmor.com/outdoor/gear/Product___40065

That leaves $85 for a backpack-- look for something in the 55-65L capacity range. You shouldn't need anymore, but since your budget is tight, I am guessing your gear could be on the bulky side, and thus you probably do not want anything smaller.

If you are set on that Eureka, then add $40 to your backpack budget with $125 I would look at Gossamer Gear's G4, SMD's Swift, Granite Gear's Vapor Trail, Gregory's Z55, Osprey's Aether 60 (heavy at 4lbs but within budget).

Any good outfitter would have the last three packs.