I've heard the Berg Vln Conc in performance a few times (once with Miss Mutter), and I have to say I'm not entirely convinced. Mutter on DG is supposed to be the definitive version, but it is full price. However,
this looks an interesting (and cheap) disc - Hartman and Janacek as well, and Zehetmair normally does really good stuff. (There seems to be a Naxos one as well, but I've never heard of Rebecca Hirsch).
I would actually recommend rather than the Vln Conc trying the Lyric Suite or Lulu Suite first - both to my ears rather more melodic (which I guess is why 'real' modernists just call them oveheated/wrought Mahler).
Verklaerte Nacht is a truly wonderful piece - but it's the other (i.e. pre-'idiocy'

) Schoenberg - so, along with Gurrelieder and Pelleas, really doesn't count in the atonal/serialist hagiography.
Good living composers? OK maybe not true greats, but John Adams, Steve Reich, Philip Glass (at least of the Violin Concerto - Satyagraha is supposed to be good too, but I've not heard it) are all excellent. I've been pretty impressed by most Gyorgy Ligeti (still going at 80) I've heard too - his madcap stuff has an awful lot more about it than most other random walks through notes! Then there also seems to be a big following for Elliot Carter (90-something now), although I've not heard enough of his to comment. Other that that I tend to go for the Finnish/Estonian axis. Rautavaara is excellent (particularly "Cantus Arcticus", "Angels And Visitations", "On the last Frontier", Anadyomene), and I've also loved what little I've heard from Peteris Vasks. Erki-Sven Tuur's Violin Concerto is also pretty impressive (or was that just Ms. van Keulen?). Some of Esa-Pekka Salonen's output is not bad either (although I do find him a bit hit and miss).
My favourite 10?
Can't do a strict order, so in on a more fuzzy ranked basis:
Rank 1: Beethoven;
Rank 2: Wagner; R Strauss; Sibelius; Mahler; Bach ( :yikes: - well he wrote so much you can leave out the most tedious 90% and still have loads to play!)
Rank 3: Adams; about 1/2 Haydn; Poulenc (never heard anything by him I don't like - must check out some more); Stravinsky
but that then leaves out other favourites like Bruckner, Nielsen, Villa-Lobos, Brahms, Rautavaara, Tubin, Rachmaninov, Vivaldi, Prokofiev, ... Mingus (

), Chopin, Liszt and Scriabin's piano music (none of their orchestral music is a patch on their piano stuff).