Improving sound of Marantz SA-8260 SACD PLAYER

I purchased the Marantz SA-8260 either in 2005 or 2006.   The sound has always been underwhelming, but the transport portion works fine. Was thinking of bypassing the DAC portion of the unit and purchasing a $200.00-$400.00 DAC which should improve the sound tremendously. I looked at the Schitt Fulla 2  $99.00,
or the Schitt model for $399.00, the Herus DAC for $350.00, or the Herus plus for $425.00.  You see where I am going with this.  Can I for $100.00-$400.00 turn this poor sounding SACD player, into a much better performer
as DACS have come a very long way in the past few years.
Thanks for your thoughts.
Yes, adding an affordable DAC would be a sensible upgrade. Just don't go wasting money on fancy "touted" cables and power cords (cheap here is just as good as expensive - unless you are a snob!).
The Marantz will function fine as a transport. Try the Fulla for $99 and if you don't like it you could easily sell it!
I used the dac on my old onkyo cd/sacd player circa 2010  for years and thought it sounded wonderful.  I tried a benchmark dac1 back around that same timeframe to compare and did not think it was much if any improvement to the onkyo so I sold it. I recently bought a new integrated amp with dac and now use the onkyo as a transport the new dac is a lot better. The last few years dacs have improved.   I would think any of the ones you mentioned would make sense. 
@roberjerman   Tough time in the Market lately? 😬 It may be a coincidence but I just read on another thread here, your decrying of investing in a phono stage.  Sometimes we really do get what we are willing to pay for! 😀
if you have Always found it "Underwhelming" and would sell it and start fresh...
It will cost you a bit more, but I use a Bryston 3 DAC, which takes the DSD feed from an SACD player over HDMI (don’t know if your player does this):  sounds great
@hifiman5: No, I don't "invest" in audio gear! II just decry the belief that too many have that 4 figure (and up!) price tags are a justification for spending more for a miniscule improvement!
@roberjerman Does the law of diminishing returns kick in at some point? Of course! The issue of how much money to spend on your rig is a personal one. We all justify different expenditures in different ways. Depending on the state of your system, 4 figures may indeed be out of line. It just depends on where you are with your system and what your priorities are regarding allocating your disposable income.💵