- Also, how much difference will 100 watts make vs 200 watts?
None you will ever notice. To get a noticeable difference takes 6 dB gain or 400 watts. 3dB is not enough to do much of anything.
Poor advice. These kind of statements tend to be made by operators that have read too much theoretical literature and don't have enough real world on-the-air experience. 3dB produces a signal that is perceived to be approximately 12% louder by the human ear at the speaker or headphones. This can win in difficult conditions.
Scenario: You own a radio that is capable of producing 200W. You're calling a DX station that at best is S4~S5. He's having trouble picking signals out of the pileup. What output level would you set your radio for, 100w or 200w? Might as well conserve electricity since it makes no difference, right? Or maybe you'd choose to be 12% louder in his ear.
An average small tribander produces about 3 dB more gain than a resonant dipole, yet given similar operator ability, will win out in a pile up 9 times out of 10.
I currently have a 100w radio (TS-890) and a 200w radio (TS-990) side by side, so I can run comparisons. From personal experience there can be large differences.
My neighbor built a monster quad. It had about 3 dB more gain than the Yagi I was running at the time. We would work JAs on 15m in the evening. When the band was wide open, S9 or better signals from JA, most Japanese operators could perceive very little difference in our signals running a KW. Usually reports were "the same" or "back and forth" between us two. As the band faded and signals dropped into the mud, or the JA station had a poor or compromise antenna, the difference became apparent. Often he was Q5 to JA when I wasn't. Does 3 dB make a difference? Depends on the scenario and conditions. I hear QRPers make the dB excuse all the time, justifying why there 5w watts is as good as (or nearly so) as 100w. Really? Not to insult QRPers. I run QRP, 100w, 200w and LL frequently. I know the difference from actual experience.
Buy new equipment, anything used on the market is way overpriced and not worth the risk.
More poor advice. Usually made by people that haven't the confidence or experience to accurately evaluate the equipment in question. I've got a shack full of equipment purchased "pre-owned" that looks new, works perfectly and that I'm not worried about failing.