Ted,
I know I'm late to the party here....someone just sent me the link to this discussion.
And, I'm going to come at this from a very different point-of-view (hope you don't mind?)
The short answer is, Yes....go-for-it!
Sell the '847, '857, '140 (and yes, maybe even sell the Flex 3000, but that's optional...depends on your personal choice, budget, etc.)....
And, buy the '7300 and '9700.... Thinking IC-7300 and IC-9700 combo. Not a huge investment, around maybe $2600 total.
Thing is, I have to look at the fact that my FT-847, 857D, TS-140S and Flex 3000 are all still working and fine.
Others here have given you good advice / recommendations....
So, why in the world did I decide to "pile on" (certainly not to just show ego, nope...)
Well, I'm not an SDR fanboy....I don't own a '7300, 7610, nor '9700....and likely never will. (but, I do not think they're somehow "evil", nor are leading to the downfall of ham radio....nope, they're just not my cup-of-tea)
But, I think you, and more importantly everyone that surrounds you on-the-bands, will be very happy you "upgraded">

You see, in today's standards of ham radio transmitters, the IC-7300's transmitter is pretty good...in regards to transmit IMD / spectral cleanliness it's not as good as the radios of decades ago, but by todays standards, it's good!
And, the FT-857d is one of the worst in regards to transmit IMD / spectral purity made in the past 40 years (see Nov, 2004, QST) With the '847 and '140, both just a couple dB better (but still pretty bad)....and the TS-140 is notorious as splattering worse if you have the processor on (I've heard it recently on 80m, and it can be rather unpleasant)
{btw, the Flex 3000 isn't bad....close-in, about the same as the '7300....but the '7300 is better on the higher-order products..}
So, like I wrote up front....taking a different view of things....yes, go-for-it! Sell the '847, '857d, and '140....and buy the '7300 and '9700.
And, have fun!

73,
John, KA4WJA