The Valencia, the 19, et al, are the great Altec speakers. The only problem is that we don't all have the space (and/or the approving spouse) to plant a pair of junior refrigerators in our living rooms. The beauty of the Bolero--and particularly the 890c culmination, where they perfected the driver--is that it very closely approximates the trademark 3D technicolor Altec VOTT sound in a manageable @25" x 15" package that doesn't require a forklift to move around.
Sound quality, of course, is highly subjective; there are so many factors that will influence one's decision as to which speaker sounds better than another on any given day. I have auditioned the Segovia quite a few times over the years through different systems with varying degrees of satisfaction. The Segovia is a fine speaker, but to me it doesn't sound like an "Altec" in the way that the horn-equipped Bolero does.
To delve into geeky minutiae for a moment, the 890a & 890b have the amazing 3000g horn tweeter, but the high crossover asks too much from the driver in those model variations. The 406-8Y in the 890c has a larger VC than its predecessors, and while the outsourced Heppner horn in the 890c (made in Chicago; not in Japan as is commonly cited) may not by just a shade be quite as sensitive as the earlier 3000g, the glorious midrange of the 406-8Y trounces the earlier 406a/406z and makes for a better listening experience with the 890c by comparison.
I have owned all variety of hi-fi gear and nearly all of the high-end Altec speaker models at one point or another, and at this stage of my life with a moderately-sized house and a wife & two young daughters (read: no more man cave lifestyle), the Altec 890c is perfect.