Alternatives to Dunlavy speakers?

A product line that is conceptually very similar to what Dunlavy was doing is PBN audio's "Montana" series.

http://www.montanaloudspeakers.com/

The big Dynaudios mentioned by Rcprince are unique in their use of two tweeters, one above the other. This effectively preserves the wider-than-it-is-tall radiation pattern of the vertically spaced midranges and woofers. The result isn't really a line source, but it does produce a more uniform radiation pattern than the Dunlavy/Montana vertical symmetry around a single tweeter.

To Audioguy -

Thanks for the additional information on the Montana's.

It is my understanding that the XP uses first order filters everywhere except on the tweeter, which uses a third order high pass. I don't know about the crossovers in the rest of the Montana line.

Just for the record, John Dunlavy's negative characterizations of vented enclosures do not apply to all vented alignments. Along the same lines, if I were to characterize all sealed boxes based on the transient performance of a Qtc = 1.2 alignment it wouldn't be a fair generalization. There are vented alignments that exhibit superb transient response, comparable to that of a critically damped (Qtc = .5) sealed box. In my opinion, Dunlavy's stance on the innate superiority of sealed boxes is a bit dogmatic. I say this as a moderately experienced amateur speaker designer and builder (over 55 systems including sealed, vented, passive radiator, isobarik, pressure relief, transmission line, and dipole. I'm currently working on three systems: a dynamic dipole; a transmission line variant; and a well-damped, ultra-slow-rolloff vented alignment).