For your needs an emissions type tester with shorts test is all you need.Matching for power tubes needs to be done by current draw,not by gm.I have a very good Triplett 3444 and a Weston 981-3,both are gm testers and the most reliable test feature is the shorts and gas tests.Although the Triplett will give me current measurements,I prefer to match power tubes in an amp that gives full working voltage.Tube testers dont give full working voltages.I have been repairing and building tube amps for over 30 yrs and the only reason I have the testers I do is for my personal collection of NOS and old stock tubes I have.But the only true,final reliable test is in the circuit the tube is intended for.You can get a good reliable emissions tester for under $100 on ebay,its really all you'll ever need.I like my testers for more of an informational type thing,but as i said earlier,the only true,reliable test is in the circuit the tube will be used in.