Hi Mike I have owned two 7300's plus the FTDX3000 a few years back, just recently sold my backup 7300 and bought the FTDX10, I also own a 7610, I kind of get what your talking about with the high frequency hiss plus RX noise in the front end of the 7300. First off to make the 7300 more listenable I use the NR all the time set between 3-4, I also don't use the pre amp 1 on 15m or below unless I am trying to copy someone really weak and the band is going our but when the pre amp is on it add way too much noise to the RX even with the NR on, this is a shortcoming of a radio that sells in the kilobuck price range plus trying to cut off audio frequencies seems to roll off what you really hear. I also use good headphones or something like the heil Boom/headset IC but have replaced the earpads on all my headphones with good replacements off Amazon (adds to comfort for long hours in the chair). The 7610 is in a different league as far as audio distortion products, yes it does have some high frequency hiss but again a little NR goes a long way plus the audio itself is way cleaner than the 7300 ever was besides I have compared those two radio's side by side and to my ears with headphones there is a BIG DIFFERENCE. I am not trying to knock the 7300 but you get what you pay for plain and simple.
Now to the FTDX10, the audio of this radio is a cut above the FTDX3000 I had, its fuller and cleaner, not as clean as the 7610 but dam close plus you also have a bass, midrange and treble that you can extend +-6db or 18db. It seems like Yaesu got smart on this baby and added a great receiver to a clean audio chain, I am not sure what the THD spec will be until the ARRL gives a lab review but for its price range its dam good. The selectivity on CW is a notch above the 7300 and below the 7610 but when tested with a signal generator pupped into the RX its dam good, they all are a cut above many radio's that came out 10 to 20 years ago. The selectivity controls are different were you have shift and width instead of twin pass band tuning so when coming from an Icom you should switch gears in your head to adjust. The NR does have some audio artifacts but not as bad as the underwater sounds from the 3000 and I feel as time goes on maybe Yaesu engineers will address this in a firmware upgrade on the 10 and the 101.
I could not tell you on the 101D I have only sat in front of one once when it first came out but am told they have had many revisions since day one so buy new not used here unless its 3 months old but beware Yaesu doesn't honor the warranty if your buying a use radio from someone, there warranty is 3 years to original purchaser and non transferable, Icom's one year is.
The con of the Yaesu is the display its not as pretty as the Icom's, the spectrum speed has no real adjustments and real time so its kind of grassy but its larger than the 7300 plus has DVI out. The 3D display to me is a frigging joke but the spectrum display is usable, like I said the Icom is nicer but if your the type of ham who buys a radio because it has a nice GUI well enough said cause this radio's RX is top notch and to me the RX is much more important than the GUI.
BTW the one thing I like also about the new Ten for its price range it has similar controls like the 3000 had, IPO/Pre1/Pre2, three stage ATT 6/12/18db, APF which is IMO almost as good as the 7610's, adjustable AGC, a fine tune button also contour control for audio peaking or dipping, I also like the second tuning knob behind the main tuning knob which lets you QSY fast up the band. The radio is around the same size as the 590S I once had maybe a little higher but not as wide but larger than the 7300. Yes I like my new backup which I seem to use more on CW these days plus the relay is not a clack box like the 7300 was. I feel that Yaesu put this radio out not to compete directly with the 7300 but to give the hams a cut above with allot more radio performance for the dollar invested, the Icom was the first entry level knob style SDR the Yaesu IMO was the first Entry Level Competition Grade Superhet Hybrid SDR, they both have there place in the market today.