Think I've used every pack mentioned so far.
If one has no more than $100 to spend, the surplus Marine ILBE packs are about as good as you can get. Having said that, they are compromised in quite a few ways and would not be the first choice. A properly fitted civilian pack would be a much better choice.
The desire and following advice to have two different packs is about as f'ed up advice as I've seen here. Buy a solid pack then use it.
