I doubt they will come out with a 24x, just like 52x cd burners, they topped out. Besides the market moves to the blu ray soon. 16x DVD's are out but arent plentiful and are expensive. At 4x, my LG burner takes 13mins to create a full DVD. At 16x it'll be about 1/4 that time. Therefore there is no point for a 24x. Go for the 16x, they are great prices right now and they are fast enough.
AMD Athlon 64 3500+ [939 Socket] W/ ASUS \"A8N-SLI Deluxe\" nForce4 SLI Chipset PCIe Motherboard
Kingston 1024 MB [512MB X2] DDR-400 PC3200 Memory
MSI Nvidia GeForce 6600GT 128MB DDR3 128-bit PCIe
Western Digital 160 GB 7200 RPM 8MB Cache SATA Hard Drive + WD 120GB 7200 RPM IDE HDD
LG Dual Format/Double Layer 16X DVD±R/±RW + CD-R/RW Drive