Yes..you should buy an acoustic. My students who play on digital pianos have a variety of tone-production deficiencies that include a generally "lighter" touch, and lack of understanding of "sympathetic" string vibration of unmuted strings, which creates pedalling woes...
If you want a good piano, for cheap, check out an older large upright piano... not all are good, but the good examples are really good sounding if well maintained. The ones to look for are genereally pre-war... 1905-1915 and have been regularily maintained.. Remember, that american spinets produced after the 2nd world war can be among the worst pianos ever made.. steer clear.
things to look for in the old big pianos
1) owned in a consistent climate
2) Make sure that it has not had a poor re-keytopping job. if the tech was careless, the keys were probably not surfaced properly, and the thicker plastic tops will make the keys too tall (check for proper key dip, black keys should not dip below white keys)
3)Strike the low octave firmly. A wooly muffled sould indicates tired old strings (you do not want to pay for a re-stringing)
4) run your hands over the tops of the hammers with light pressure, feel for any side to side play which indicates loose center pins.
5) If possible, look for cracks in the pinblock (very serious)
6) play a high reble note repeatedly (40-60X) quickly to check for pin bushings that swell with friction heat (repitition will be compromised)
7) Have a tech come with you if the piano has passed all of these tests, for a finaltest to check for regulation progblems
Now, if you want to spend some real money...
I just bought a Seiler Upright and love it, the bass and treble sections are "exciting", not lifeless, I must agree that japanese pianos must be large in order to really have the power needed for high-level playing.
As a technician, I cannot argue the overall reliability of yamaha, as long as it is not a brand new small upright (not made in Japan)
Yamaha uprights are the "toyota" of pianos they will get you there safely, and uneventfully, and you will get good resale, but it is no mercedes.
Chinese pianos are genereally bad...especially for heavy use applications. I have repaired far too many actions on 10 year old pianos from that neck of the woods. hope this helps