Well, I can get pre-seasoned tri-tip for about $3.5/lb... I'd go with these, as at this price, there's not much cheaper, they are very easy to cook, and taste great...
I typically cook at about 250F, until internal temperature is roughly 130F, maybe 135F, but it just depends on how people like their meat. Time... well, you should probably practice one before doing a bunch, but I'd say 45 minutes to a hour. Personally, I don't feel any need to 'sear' them at all, but you could sear, if you really wanted, just pull them a little earlier , like 120F, and sear until desired internal temperature.
These can be cooked hotter, and will take less time, without really any detrimental effects, I cook them lower/slower to get a bit of smoke on them.
Obviously the price I can get these for is on the low end of what Tri-Tip costs... but Personally, I'd probably still go with Tri-Tip even if I had to pay $5 or so... very little fat or waste, and if done right, it's darn near as good as any other cut of beef.
Darn, now your making me think I need to make a trip to A&A market II ( the original burned down) to get some Tri-Tip for this weekend.