I'm gonna second all of these ZT suggestions. I think the 0200 is a badass blade at 4". The 0350 is also nice, but it's blade is .75" shorter and .035" thinner. Their line is fantastic. I had my share of liner locks so I thought I'd splurge for one of their frames which is probably way over your budget and I though it'd be over mine too. But after scouring the secondhand market for a month or so I came across a 0301 on a different forum for $130 :thumbup:... and then a few weeks ago I noticed on went on here for $90 :thumbup::thumbup:. So keep your eyes peeled and start practicing typing "I'll take it" for speed haha.
Ooh, and how about that new 0550? Loving that ZT line...