The Thiel Dealer I visited recently is also a Musical Fidelity dealer, although he was demoing the 1.6 with Rogue monoblocks, and they sounded fantastic in that setup, MILES above a B&W 603. The Thiel 2.4s are much more authoritative but in another price range.
I think with that low standard (B&W 6 series) of entry the Celius, Theil & Magnepans (as long as you dont want very large dynamics) would be a huge step up. The Celius 202 would probably have the most impressive bottom end of that list, but I think the other two have better mid-ranges and overall clarity and coherency (I have heard all three but not side by side). One other caveat about the Magnepan's is they do need careful placement and perhaps room treatment to get the very best out of them as they are dipolar (radiating sound front and back), but will sound great if setup right.
For what it's worth I'd add the Totem Hawk to that list, which was The Absolute Sound's pick in that price range over the others you mention, and although not as efficient as the Thiels would still be easily driven by your MF amp as long as you are not looking for 110db levels.
I think with that low standard (B&W 6 series) of entry the Celius, Theil & Magnepans (as long as you dont want very large dynamics) would be a huge step up. The Celius 202 would probably have the most impressive bottom end of that list, but I think the other two have better mid-ranges and overall clarity and coherency (I have heard all three but not side by side). One other caveat about the Magnepan's is they do need careful placement and perhaps room treatment to get the very best out of them as they are dipolar (radiating sound front and back), but will sound great if setup right.
For what it's worth I'd add the Totem Hawk to that list, which was The Absolute Sound's pick in that price range over the others you mention, and although not as efficient as the Thiels would still be easily driven by your MF amp as long as you are not looking for 110db levels.