The  htseq_bams_to_count_matrix tool in the test toolshed might be worth a try - it creates tabular count matrices from any number of individual sample bam/sam files (it is NOT read group aware!). Each row contains the count for that contig for each sample. It uses HTSeq code and you supply your favourite gene model as a GTF file for defining the regions to count and how to amalgamate - eg count reads overlapping exons and sum those into total counts for each gene. Please give it a try. Install from the admin interface and let me know how you get on. There's a companion tool differential_count_models  also in the test toolshed that includes edgeR, DESeq2 and VOOM from Bioconductor - it runs 1 or 2 way GLMs using the count matrices generated by the htseq tool - be warned that it takes a long time to install everything so be patient and allow 20 minutes or so for the installation to finish because it compiles and installs R 3.0.1 and Bioconductor packages.