Should I try to improve speakers at $2000.00 range


System:
SPEAKERS...Celestion SL700SE...old but Like new
AMPS...Quicksilver 90 watt silver monos
PREAMP...Quicksilver LS non-remote...new model
DAC...Rega...Theta Miles as transport
CABLES... Kimber 8tc/8tc bi-wire (speakers), Kimber kcag and silverstreak (interconnect), Kimber 75 coaxial (Miles to DAC)
zoot45
...Had been long time in desire to listen to Nola Contender with powerful tube amp such as QuickSilver M90.
The new price is exactly $3400 I've mentioned in the previous post.
Another way is to wait to double your upgrade budget and shoot for Nola Viper II.
Nice system.

I guess if I were you, I would buy some used Merlin TSMs, and see what I thought. I'd then sell either the TSMs or 700s. If you liked the TSMs better, you could probably upgrade them later as well.
If you like why change? How do you know you would enjoy a change? And since already happy why risk it?
Improve is hard to say but you can certainly go for a lot of different sounds for $2000. If you are asking, chances are you will consider at least some to be improvements as long as you match to amp and room well. the devil is all in the details.....
I tried a number of speakers, at a lower price point than yours, but ended up with a pair of Snell K/IIs. Liked them so much, I grabbed a pair of J/IIs off Ebay and couldn't be happier. Older isn't necessarily better, but sometimes old can be very, very good.