Knowing your budget and your needs and desires, including the speed of your Internet connectivity, would be helpful.
In my opinion, you shouldn't buy anything with less than 16 MB of flash and 128 MB of RAM at any price (you can hit those marks at or below US$20). Once out of budget-level units, you should have more than that for getting more than a couple years of life out of it.
With demands of more than 50-100 Mbps or running anything other than basic routing, if your budget permits, you should consider recent multi-core, ARM-based router, or an x86 and a separate AP (which could be a moderate-price all-in-one, wireless router).
Here's one excellent place to start with a "short" list (and the posts following)
(Though later posts reinforce that the Archer C7v2 and later aren't a "good value" in the market any more.)