I was accepted last year to Carnegie Mellon's Literary and Cultural Studies PhD program straight from undergrad....it can be done!
I was an English major with minors in Econ and Polisci, I think my English GPA was around 3.95. I was also in the Honors Program, which helped.
The GRE's are such bs. I got an 1140 on the general test, and the subject test in Literature went horribly. I think I got a 560 or something. From my understanding though, the grad admissions committee doesn't put too much emphasis on the subject test....for crying out loud, it's on 1000 years of Western literature!
The fact that I did an overseas research project in London the summer of my junior year, and studied abroad in London, definitely made me stand out (my field is 18th century British lit). Also, I knew exactly what faculty I wanted to work with at CMU, and our research interests are practically identical. She's now my advisor, and kicks major ass.
Believe me, I understand your anxiety....senior year of college was so stressful. All my friends were out at the bar while I was in the library writing my thesis, applying to grad schools, and generally freaking out. Honestly, I think grad schools are a crapshoot, but I would advise you to apply to programs that fit *your* interests. CMU was the last school I applied to, and I remember I just got a really good vibe from their website and the program itself. If anything, you'll have a better chance of getting accepted to schools where you can envision yourself being.
Basically, I didn't do that great on the GRE's and still got into a good program. Focus on your writing sample and your personal statement....these are probably the most important things schools look at, and they are the things you have the most control over. Hope this answers your question, and good luck! You'll be fine