Well just in case you are in the UK, and for any others wanting about the best quality +RW, in fact any type of rewrite disk money can buy SVP are now doing the 8x Ricoh DVD+RW disk.
They also have, for the smarter buyer http://svp.co.uk/product/philips_branded_8x_high_speed_dvd_rw_philips038 the same disk but with a Philips brand on the face of the disk.
The disk top may not 'look' as nice (IMO) as the Ricoh version, but its the same MID/disk build RICOHJPNW21 and that is the important part.
As asked for by the OP ...SVP also have the 4x version http://svp.co.uk/product/ricoh_4x_dvd_rw_ricoh023 I have never used these so cannot offer any info about them, they are not the same MID using RICOHJPNW11 but its a close number and I wonder if its worth a go. The W21 versions can only be burnt at 6x or 8x and I might give them a go at Â£4 and change for 10 of them (about the same price as the 8x).