classical newbie

There are several record labels known for high quality sound for Classical music; look for Decca, Naxos, Teldec, Telarc, Chesky (uses their own proprietary system for remastering great performances), Chandos, harmonia mundi (France) and Philips to name a few.

For essentials with outstanding sound, I highly recommend a Tchaikovsky collection of Symphonies 4, 5, 6 on Decca (Valery Gergiev/Vienna Philharmonic), "Berlioz: Orchestral Works"...Colin Davis/London Symphony on Philips (ADD) and includes "Symphonie fantastique."

Essentials also include Bach's "Brandenburg Concertos," Mozart's symphonies and concertos, anything Haydn, Schumann, Mendelssohn and Beethoven. The Amazon reviews are very helpful.

There are excellent sounding Beethoven box sets such as Daniel Barenboim/Staatskapelle Berlin on Warner, Zinman and the Zurich Tonhalle on Arte Nova... 2 very different interpretations of LvB. For Brahms, look at Guilini's "Brahms: The Complete Symphonies" on Newton Classics.
For the best in sonics look for Paavo Jarvi's Beethoven; SACD-DSD on RCA Red Seal.

Also if looking for great sounding SACD, there's Michael Tilson Thomas/San Francisco Symphony on their own label, SFS Media.

Mechans...LvB is the great Ludwig van Beethoven. I see now it was not a very coherent statement, but I was saying that there are many affordable box sets containing all 9 symphonies. Many conductors will record the complete Beethoven Cycle with a particular orchestra; he may be the Principle Conductor of the orchestra or a Guest Conductor and the record label will package them into a box set.

Daniel Barenboim's style is a slow, romantic interpretation of Beethoven, whereas David Zinman performs Beethoven at faster tempi which closely resembles the way the composer intended the piece to be performed. (by using the tempo and metronome markings written into the score).

That's why I own about 10 different cycles of Beethoven; each conductor has his own interpretation, also some utilize a large orchestra, some use a small ensemble which is more historically accurate to the period in which it was written.

Rja... We had a long discussion a while back regarding which is the best Karajan/Beethoven cycle.

IMO and many others, the 1963 BPO cycle is the best, but it sounds like 1963.
There's the 1977 BPO cycle (ADD) which feature excellent performances, but it has that DG close-mic technique which I find a bit harsh sounding.
Lastly, there are the Vienna recordings (DDD, 1980s) which had such poor early digital sound that Karajan himself ordered that they be remastered and re-released. These have a good open sound and the Vienna plays very well, but as a whole, they are not as good as the first 2 cycles. (Karajan by this time was in his 70s). I like these remastered disks due to the unmistakable sound of the Vienna Philharmonic. I believe these are the only symphonies on CD that you can buy individually.

But now we have a remastered SACD box set of the 1963 Berlin cycle which is excellent.
http://www.amazon.com/Beethoven-Symphonies-Gundula-Janowitz/dp/B0000C03AH/ref=sr_1_12?s=music&ie=UTF8&qid=1386312070&sr=1-12&keywords=von+karajan+beethoven+symphonies

Expensive, so I bought mine used and now it's the only Karajan LvB that I play. Needless to say, I'm a Karajan fan.

update...I see that there are now some single SACDs from the 1963 cycle; these are the ones to buy if you want a taste.

String quartets/quintets on the Naxos label is an inexpensive way for a newbie to explore chamber music. High quality DDD Redbook.