Strictly speaking for a rock player in 1968(the year I started playing bass, actually), what would be "the" amp to have would depend on whether you were a well-known pro, a local hero bar band type, or still in the garage with hopes of playing a school dance or church social in the near future(although everyone in each catagory would want the coolest stuff). In this pre-SVT landscape(and The Acoustic 360 was just barely emerging), I would have to say a Sunn 200s(or 2000s later in the year)or Kustom 100 or 200 head with a 2x15, or possibly 3x15(if you could swing it)cab. Perhaps a silverface Showman with the larger JBL loaded cab. Anything else was a distant runner-up. Sure, there was plenty of other gear out there at the time, but if you had unlimited funding, those three were the styling rigs to have, and the Showman barely qualifies, trading on the clout of the Fender brand name. Bass players in the know ditched their Bassmans for the higher-powered Showmans, but in either case the speaker cabinets were terribly inadequate with their 12" depths and lack of any serious porting. By that year, if not earlier, Vox(the American-made, Thomas Organ stuff)had really fallen out of favor, after three years of British Invasion associated hype had passed and players wised up to the fact that they were poorly designed over-priced junk. If you saw anyone playing a Westminster bass rig(with the 18" cab)or a SuperBeatle, it was because they got a good used deal on it, or it was a hand-me-down from a big brother. The very look of those amps was becoming passe. The larger solid state Standels were creeping in, even used by some 'big' names like the Blues Magoos or(I think)the Lovin' Spoonful, but they never really caught on in a large way. Marshall bass stacks were very hard to come by in the US(and not that great for bass amplification anyway), so hard to come by that even that brand's greatest endorser had to use other gear in the States. 1968 was all about Jimi Hendrix. As rock band tour logistics were barely considered in those days, getting his Marshalls to his American gigs was always an iffy proposition. A very 'forward' Sunn promotions guy talked the JHE into a sponsorship of gear for the spring '68 tour. However, what made Sunn amps such superior bass gear(for the times)didn't translate to guitar. Innovative low frequency enhancing cabinet design, crystal clear ultra linear amps with KT88's, beefy construction certainly made Noel Redding happy, Hendrix, not so much. But Redding, as one of the highest profile bassists in this new era of rock, always had his wall of 2000s behind him. The Who, The Buckinghams, Steppenwolf, Jefferson Airplane, CCR, The Grateful Dead, It's a Beautiful Day all had some sort of Sunn bass gear at that time. Otherwise, Kustom, with their flashy tuck'n'roll and low maintenence solid state heads, reasonably constructed cabs with round ports(and who could resist that 3x15"?)became the Pepsi to Sunn's Coke. While the Doors became the poster boys for Acoustic, they really didn't have a bass player, did they? While '68 breakout bands like Spirit did use Acoustic backlines, it was only when JPJ/LZ and Rick Gretch with Blind Faith toured the 360 in 1969 did that amp become legendary. Guild amps like the Thunderbass were rarely seen beyond the east coast. In '68, Ampeg was just emerging from the fallout of ousting the rock-hating founder Everett Hull(with his accordion amps), and had a lot of catching up to do with the then-current marketplace of big cabinets and big wattage. I think they got it sorted out eventually. British companies like WEM and Sound City/Hiwatt were barely known of in the US that year. Gibson was a non-starter, almost as fuddy-duddy as Ampeg had been. I don't think Traynor had any serious US distribution until '69/'70.