I've designed -60 dB and -80 dB resampling filters today. The first one is 48-tap one (and more when downsampling), is oversampled 32 times, so the half-width table has 768 coefficents. The second, high quality one is 64-tap and is oversampled 128 times, which yields 4096 coefficents in the table. Both filters have 3 dB attenuation at 0.45 of sampling frequency and respectively -60 or -80 dB at 0.5 of sampling frequency. I've also made siginficant progress on resampler reference (not optimized at all) code, but it is not yet finished.