I have Trace Elliot 1x15 and 2x12 horn loaded cabs which sound great with my old AH250 head.
I have just started playing again after about 5 years out and my back is feeling the strain of oiking the Trace cabs about to and from rehearsals.
I have checked out the lightweight Vanderkley and Bergatino neo speakers and diddy 1200 watt amp but once I had regained consciousness again after finding out the price (the fat end of £2.5K) I had a brain wave..could I replace the Fane speakers in the Trace cabs with neos?
I have looked on the web at the Eminence Basslite Series and was also contemplating the Celestion 12" Orange labels for a more punchy sound (or even a combination using the Celestion Green label heavier, warmer bottom for the 15).
Does any one have any experience of retrofitting neos into their existing cabs or have a preference for any other make of neo speaker on the market?

I wouldn't bother, the cabs themselves are heavy without the speakers in, and you will need to know the TS parameters of the speakers to accurately model them and ensure the correct match between cab and driver.

Take a look at Ashdown or Markbass for more cost effective neo cabs. Or Purple Chili (Mike of Iceni Zoot fame) which are excellent value for money :)

I agree with Merton, been down that route, more sound efficiency is better. I am still old school in trouser flapping moving air, but just use small light cabs for a tighter sound and reinforce the sound with good mixes and projection through a PA. My 4x10 I leave at rehearsals and mostly use a small 1x15 for gigs D.I'd. No bad back anymore!

You could also look at PJB Cabs. I use a PB300 Powered Cab with a Flightcase Combo. This is 10 x 5 inch Neo Speakers and 400w of the cleanest, deepest bass imaginable. You can pick the whole rig up for about £1200. I use mine to effortlessly to power all the low notes in a (bloody loud) 8-piece soul band. The cab is a one-handed carry.

Thanks for the good advice chaps.
I have looked into the specs of some of the "replacement" speakers primarily for my 15" cab, and weight aside, I'm thinking that to me my current set up sounds great - I know lots of bassistas really don't like the TE sound but it floats my boat!
Plus the trade in value/current S/H prices on TE are gash so would work out proper expensive to replace the lot, (even though I have had the green light from the missus to do so) it would break my heart to give my "old faithfuls" away for next to nowt.
Looks like I'll just have to have that extra Shredded Wheat and start to workout lol!
Seriously, I think that (lottery win excluded) I'm just going to tough it out with the Trace weight syndrome but I am investing in a foldaway sack trolley which may help a little..a lot cheaper too!

I have a 2x10 and 1x12 vanderklays for sale if you are interested?

PM sent.