bmw583,
The 340's are 5 db higher in efficiency...a big margin for HT playback of THX reference audio levels! I'm looking at the 340's and 200's for a 5.1 setup with 90-95% HD-DVD movie views in a big romm (5kcf), so believe the 340's will work better for me!
However, with a smaller room than mine and using a beefy amp with plenty of dynamic headroom, you may find the Sierras's playback levels perfectly fine for HT!
Ted
Sierra RAAL V2 Towers, Axiom EP 500 Sub, Morrow SP7 Grand Reference Speaker Cables, Phillips CD880 XLR Balanced Variable Line Output to Orchard Audio Strakrimson 375w/per ch Stereo Ultra GaNFET Amp..... (Dedicated 2.1 Acoustical Music Listening Room)!