Hi! i have listened to a lot of tuna, including what you have, and what you want to hear. all that you mention i think provide top-notch sound. (except the only fishers i have heard are the earlier mono units w/a relatively modern studio-12 decoder; and the scott i owned was a foster blair modded 310d/335mpx. i also owned a mac mr65b completely refurb'd modded by stephen sank - a thing of beauty; and sounded good to boot! acccording to mr sank, completely refurb'd/modded 65b/67/71 are too close to really say one's better or worse than another.) regarding the tubers, to my ears, the sherwoods - both mono w/modern outboard mpx, and stereo; are the best sounding tubers i have heard. best reception, as well. never heard the marantz 10b, but i have heard the 20 inside an 18 receiver (two iterations, one refurb'd by mike williams). considering some say the 20 is better than the 10, i'd stick w/the sherwoods. regarding the s/s units, i must first of all state that i find the mac s/s tuna unlistenable. i had a mint mr74 and a completely refurb'd mr77, and they were one of a select few tuna i could not consider a quality listening source. never heard a 78, but since most folk who've compared say the 74 & 77 are sonically better, i have no desire to hear one. regarding the others you mention, i have heard all except the tu919, and i find them all superb. (i still have a marantz 18 receiver and a tag mclaren t20, which is a slightly tweaked 8000t.) i also think the revox b261 is every bit as nice as the b760, in spite of that the tic "shootouts" say about it. and the b260 is also in the same league. re the da-f20 and the tu-9900, i had two of each, one modded, one never serviced. stock, i preferred the da-f20 to the tu-9900 modded, the tu-9900 was better than the modded da-f20. i can't say if unit-to-unit variability played a part regarding the stock units. i do know i did not like the fact that the mitsu doesn't have a blend circuit for less-than optimal signals. i also have a modded refurb'd tu-x1, which is a fine thing indeed. worth the money for the sonics and reception? honestly, only if you're a collector. in hindsight, i should perhaps have sold the tu-x1 and kept the modded tu-9900 - the sonics were so close, and the looks and size of the tu9900 are far better than the mammoth tu-x1, imo. all the tuna you mention wanting to hear - Marantz 20/20B, Revox B760, Audiolab 8000T, Philips AH6731 - are all fine sounding, imo, (the marantz noticeably less sensitive of that bunch, imo), but would you actually prefer any of them to what you already have? i think you might, but you have to try it and hear for yourself! also depends on the rest of your system, and whether you favor extreme detail, slightly warmer, etc. for example, i found the revoxes to be extremely detailed, a little on the drier side. same w/the mitsu. the philips and the tu9900 and the audiolab less so; and the accuphase 100/101 even less so; perhaps w/a tiny loss of detail. regarding what you have heard and let go, my st-a6b is a killer, but it's been modded and refurb'd. i loved both the t100 and t101 i had, but i can't really say one was better than the other - both excellent, w/the sound leaning to the organic. i had a modded accuphase t109, but my modded hk 18 was slightly better, w/a taller soundstage; otherwise they were equal. for my ears, the best bet for the money is a modded refurb'd hk citation 18. (possibly the same goes for the 14 & 15 - same sonic signature and still extremely nice even in stock form.) can be equaled, but not beaten. also in this category - great sonics, reasonable scratch - modded rotel rht-10. and the rotel has the best reception i have encountered - a smidge better than all my good, quality s/s tuna, which i have found to be pretty comparable. except, of course, for the sony xdr-f1hd, which has the best reception of anything. (imo.) too bad it sounds so mediocre. and only ok after extreme mods. regarding the rht-10 - this is a tuna that screams for mods and refurb. stock, it is merely excellent, but not a standout. best tube sound? any mono sherwood after the s3000ll, w/quality modern s/s mpx. or a stereo s3000 iteration, if my refurb'd mildly tweaked s3000v is any indication. (i've never heard the earlier pre-s3000ll iterations; they may sound as good, or better, w/less selectivity.) easily as good as the best s/s, imo. doesn't sound "tubey"; just extremely smooth, accurate, extended dynamic sound. better than the beautiful totally rebuilt mr65b, better than the mono fishers or scotts. imo, of course! enjoy your tuna fishin'! doug s.