I agree, for aleatoric, Lutoslawski (specifically, Sym. 3) is a great example. Plus, it's notated in standard notation (unlike Penderecki, who invented his notation), so you can achieve the same effects for a studio session without having to explain new notation.
I have to say, I also love scoring that is a) cinematic/narrative, and b) really clean and clear with the foreground/middleground/background. Right now, I'm saturating myself with the following three categories:
1. The Russians. Tchaikovsky (esp. the Nutcracker and Sleeping Beauty full ballets, and Sym. 4 and 5). Rimsky-Korsakov (Especially after reading his orchestration manual). Early Stravinsky (Firebird and Petrouchka). Dvorak's 9th. Prokofiev's Romeo and Juliet suites.
2. Film scores. John Williams. Star Wars, Harry Potter, and Superman. I'm also transcribing cues from Jerry Goldsmith's Star Trek, and Danny Elfman's Spiderman. Incidentally, I highly recommend you all try that. Transcribing an orchestral cue by ear is (IMHO) the single best way to learn orchestration. You're basically reverse engineering doublings and orchestral balance.
3. For the lighter stuff, Mendellsohn's Midsummer Night's Dream, and the Hebrides Overture. Really brilliant light writing for strings and winds.
I think those are fantastic scores to get into your collection and walk through.