Some of my favorites have already been mentioned above, but here are some of the preamps and amps I like best, followed by those I don't much care for:
Best looking preamp/power amp combos from same manufacturer:
1. Hovland (HP-100 pre and Hovland Sapphire amp)
2. Classe Omega Mark 2 preamp and power amps
3. YBA "Passion" series (in silver)
4. Pass X-2.5 preamp and XA-150/200/300 series amps
5. Spectral DMC-12 preamp and DMA-100S power amp
6. Accuphase (sumptious quality and finish on their whole product line)
7. Rogue Audio R99 preamp and M120 monoblocks
8. Ayre K-5 pre and V-5 amp
9. Aloia pre/power combo
10. Mark Levison Reference Pre No. 32 and No. 336 amp
11. BOW Technologies ZZ Reference series
12. Bryston BP-25 pre with 4B-ST or 14B-ST power amps
(with 17" silver faceplates; amps without handles)
Best looking preamps:
1. Conrad-Johnson Premier 16 and 17 Series, and ART
2. Klyne 7LX
3. Bel Canto PRE6 (multichannel)
Best looking power amps:
1. Linn Klimax 500 Solo and Twin
2. Jeff Rowland
3. Kora Concept Cosmos monoblocks
4. Art Audio PX25
5. WAVAC HE-833 SET
Least attractive preamps:
1. Hafler DH-110 (I owned one and it did a good job for the money, but it looked a piece of equipment in the armored personnel carrier I had as a unit commander in the Army)
2. Nagra PL-P
Least attractive power amps:
1. Manley Snappper and Stingray; Manley Steelhead phono
2. HeadRoom "The Max"
3. The Hafler DH-200 and DH-220 (I owned one of each in the early 1980's and thought they were a good value, but they sure weren't much in the looks department)
4. Niro (the one that looks like a cross section of a jet turbine)