Just to finish up this thread I got my answer today. So, in answer to Red Spade's question the speakers are from different manufacturers. The speakers spec'd at 92db at 1 watt at 1 metre were a pair of Polk DB6502 component 6" car speakers. They are (were) fitted to the front doors of my car and powered from a Sony head unit with has probably 20 wpc rms. I paid good money to get them fitted, should have done it myself as the fitters didn't seem to know about phase of tweeters and mid bass, didn't know about connecting all wires to the crossover box and didn't seem to care too much about fitting the speakers to the door frame so there wouldn't be any gaps. The phase and crossover problems have consumed me for a few months now, given they were all messed up it took me a few goes to correct it all. In the end I hated the speakers anyway, didn't matter how they were configured they sounded average. The tweeters mounted in the car original dash locations sounded like honky midranges, very annoying and there was no top end, just lots of midrange.
I was that frustrated that I went to another car audio store and had a listen to a couple of other pairs of speakers. Hard to make any valued judgments on a sound board but in the end it came down to some Morels which were made specifically with a high sensitivity for systems without car amps and a pair of Pioneer D65C whcih are another two way 6.5 inch component speaker. To my years the Pioneers sounded the best to me but had a lower sensitivity than the Morels at 84db at 2.83 volts at 1 metre. The Morels being up at about 94 db. The Pioneers were the catalyst for my question about sensitivity. I was starting to get buyers remorse thinking that the Pioneers would not be sensitive enough and that I should have bought the Morels which were made for my application.
Anyway, bought the Pioneers and finally got around to fitting them today. This is when I discovered that the professionally installed Polks were leaking a little air around the mount. The installers hand't even bothered to make sure that they were sealed. The Polks are a 6"and the Pioneers a 6.5. The Polks have a separate crossover with a 12db slope on both mid and tweeter whereas the Pioneers have a 12 db slope on the tweeter in line and the mid bass just a 6 db coil attached to the midbass itself. Off to Autobarn to buy some spacers as the Pioneers were around 30mm deeper. After a few hours and double checking all the wiring they're all working.
The answer to the sensitivity question? Looks like the Polks are exaggerating the measurements as the Pioneers play just a little louder and also have a much fuller sound with the bigger mid bass driver. The Pioneers sound very good too. I'm glad I finally got it sorted. Shame I spent good money on the Polks and paid some dunce to fit them but that's the way it goes I guess.