[Kromm]

I agree with TBC and CR. Forget about points -- they won't help you. Extreme, Silly Example #1: Give one of your ambushers 100 points in Musical Instrument (Lyre), so he knows it at IQ+24. Now he's worth 100 points more and isn't any closer to being a threat, except in an Angbandian Idol contest. Extreme, Silly Example #2: Give one of your ambushers the Unholy Sword of Smackdown, which inflicts +1d each of fire, electricity, and cold on each hit. If it's on loan from the Dark Lord, it isn't even his and won't affect his point value through Signature Gear or Wealth . . . but it makes him a huge threat.

For an even match, simply make the adversaries' average skill, defenses, damage, and DR equal to the PCs' averages in those areas. You can probably vary one up a point or two if you vary the other downward a similar amount. To make things tougher, raise one or two numbers without lowering anything. To make things easier, drop a score or two without raising anything. Don't try to evaluate every last special consideration . . . just eyeball it ("Okay, the guy with the bow is a Weapon Master, so I had better give him lower defenses to keep him even." "Hm, the guy with the spear has Berserk and probably won't even defend himself, so I'll give him better armor to even things out.").

Oh, and one last thing: Despite all the points and rules, GURPS isn't a highly objective, prescriptive system where the roleplaying is actually a thin veil over a set of PvP rules. You cannot rely on its mechanics to gauge threats and outcomes very precisely. It's designed to be used by a GM running a game with a group of players in a more-or-less cooperative fashion, and it tacitly assumes that the GM will sometimes fudge outcomes to get dramatic results. So be prepared to do that . . . if the bad guys are getting destroyed a second after unleashing their ambush, have their cut-off group or security element show up as reinforcements, have the wizard use his "secret weapon" Lesser Wish amulet to score a critical hit, etc. If the bad guys are winning too easily, have them get overconfident and use bad tactics, or simply have one fall down if he suffers so much as a nick. Really, if you're good at thinking on your feet, you can make any group of foes a suitable match for the PCs.