I bought my fronts and center about two years ago and am finally adding in the surrounds - just bought a house. I have an Onkyo TX-SR600 receiver Polk RT55i fronts Polk CS400i center I have been very happy with all three speakers but may decide to upgrade the two fronts at this time and move them to the rear - or not. Can anyone give me a rough estimate as to where in the current crop of Polk bookshelf speakers the RT55i speakers would best compare? It seems as though the RTi6 is at the price point to be the replacement for 2002's 55i BUT it only has one 6.5" woofer and the 55i's had two. In fact, until you start looking at the LSi9 pair there are no Polk bookshelfs with dual 6.5" woofers - and the LSi9's are about $900 per pair and so about twice the cost of the 55i pair I have. Would the single 6.5" driver RTi6 be an actual upgrade from the dual 6.5" driver RTi55? Hell, moving up the ladder even further to $700 per pair would the LSi7 be an upgrade from RT55i? It would appear so from the price tag as the RT55i set were around $450 per pair IIRC. This would mean moving my dual 6.5" drivers to the rear in favor of a single 5.25" driver. . .doesn't add up to me. Help? Thanks for your time either way.